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<!--XBRL Document Created with Wdesk from Workiva-->
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  <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:type="extended">
    <link:label id="lab_us-gaap_ProceedsFromWarrantExercises_89a0044c-7fb0-4281-ba9f-1f09ea07e4cb_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromWarrantExercises" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Proceeds from issuance of common stock related to warrants</link:label>
    <link:label id="lab_us-gaap_ProceedsFromWarrantExercises_label_en-US" xlink:label="lab_us-gaap_ProceedsFromWarrantExercises" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Proceeds from Warrant Exercises</link:label>
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    <link:label id="lab_us-gaap_StockRepurchaseProgramAuthorizedAmount1_fa996c76-13db-4ff7-a361-4be278bfb9d7_terseLabel_en-US" xlink:label="lab_us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Stock repurchase program, authorized amount</link:label>
    <link:label id="lab_us-gaap_StockRepurchaseProgramAuthorizedAmount1_label_en-US" xlink:label="lab_us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Stock Repurchase Program, Authorized Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
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    <link:label id="lab_us-gaap_SupplementalCashFlowInformationAbstract_0c80f8ea-720b-4bbb-bdcb-f839b0b31971_terseLabel_en-US" xlink:label="lab_us-gaap_SupplementalCashFlowInformationAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Supplemental disclosures of cash flow information</link:label>
    <link:label id="lab_us-gaap_SupplementalCashFlowInformationAbstract_label_en-US" xlink:label="lab_us-gaap_SupplementalCashFlowInformationAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Supplemental Cash Flow Information [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
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    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract_30b055b8-0847-482e-a3dc-00d69d856021_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Changes in operating assets and liabilities:</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract"/>
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    <link:label id="lab_nmih_GainLossonChangeinFairValueofWarrantLiability_0cf6b4bf-bd32-483b-a04b-d2d45cb00bc3_negatedLabel_en-US" xlink:label="lab_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">(Gain) loss from change in fair value of warrant liability</link:label>
    <link:label id="lab_nmih_GainLossonChangeinFairValueofWarrantLiability_label_en-US" xlink:label="lab_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Gain (Loss) on Change in Fair Value of Warrant Liability</link:label>
    <link:label id="lab_nmih_GainLossonChangeinFairValueofWarrantLiability_documentation_en-US" xlink:label="lab_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Gain (Loss) on Change in Fair Value of Warrant Liability</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:href="nmih-20220331.xsd#nmih_GainLossonChangeinFairValueofWarrantLiability"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:to="lab_nmih_GainLossonChangeinFairValueofWarrantLiability" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member_4a0070a9-6725-45b6-bc07-8d217c15d027_terseLabel_en-US" xlink:label="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Corporate Headquarters and Data Facility Lease 1</link:label>
    <link:label id="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member_label_en-US" xlink:label="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Corporate Headquarters and Data Facility Lease 1 [Member]</link:label>
    <link:label id="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member_documentation_en-US" xlink:label="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Corporate Headquarters and Data Facility Lease 1</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:href="nmih-20220331.xsd#nmih_CorporateHeadquartersAndDataFacilityLease1Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:to="lab_nmih_CorporateHeadquartersAndDataFacilityLease1Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_EarningsPerSharePolicyTextBlock_e6e442eb-a24d-454f-83a9-751ce68d2a03_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerSharePolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Earnings Per Share</link:label>
    <link:label id="lab_us-gaap_EarningsPerSharePolicyTextBlock_label_en-US" xlink:label="lab_us-gaap_EarningsPerSharePolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Earnings Per Share, Policy [Policy Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerSharePolicyTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerSharePolicyTextBlock"/>
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    <link:label id="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported_5184a10a-6fb1-4f2c-9eec-fe8eea93799a_terseLabel_en-US" xlink:label="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current year IBNR</link:label>
    <link:label id="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported_label_en-US" xlink:label="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Year Claims and Claims Adjustment Expense, Incurred but Not Reported</link:label>
    <link:label id="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported_documentation_en-US" xlink:label="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Year Claims and Claims Adjustment Expense, Incurred but Not Reported</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:href="nmih-20220331.xsd#nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:to="lab_nmih_CurrentYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_652a6494-50a5-4b1e-85cf-bdfda2598066_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</link:label>
    <link:label id="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_label_en-US" xlink:label="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="lab_us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetIncomeLoss_567a0761-8556-4f55-8903-ad4500a14224_totalLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net income</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_ef1a71bd-29d5-4d1a-9876-666d1062b7ed_netLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net income</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_a85c1a2c-4d82-4633-833f-f87626f75de6_verboseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net income</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_bfc49608-4422-4c7e-8121-ee0ee6979812_terseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net income</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_label_en-US" xlink:label="lab_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net Income (Loss) Attributable to Parent</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetIncomeLoss" xlink:to="lab_us-gaap_NetIncomeLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_OperatingLeaseRightOfUseAsset_e0e11fa8-0a1a-4869-a766-59df92db507a_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeaseRightOfUseAsset" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Right-of-use assets</link:label>
    <link:label id="lab_us-gaap_OperatingLeaseRightOfUseAsset_label_en-US" xlink:label="lab_us-gaap_OperatingLeaseRightOfUseAsset" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Operating Lease, Right-of-Use Asset</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="lab_us-gaap_OperatingLeaseRightOfUseAsset" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_LoansInPoolLoanToValueRatio_09c316b2-6043-4669-8fba-b230c22d7c3a_terseLabel_en-US" xlink:label="lab_nmih_LoansInPoolLoanToValueRatio" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Loan-to-value ratio (less than)</link:label>
    <link:label id="lab_nmih_LoansInPoolLoanToValueRatio_label_en-US" xlink:label="lab_nmih_LoansInPoolLoanToValueRatio" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Loans In Pool, Loan To Value Ratio</link:label>
    <link:label id="lab_nmih_LoansInPoolLoanToValueRatio_documentation_en-US" xlink:label="lab_nmih_LoansInPoolLoanToValueRatio" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Loans In Pool, Loan To Value Ratio</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_LoansInPoolLoanToValueRatio" xlink:href="nmih-20220331.xsd#nmih_LoansInPoolLoanToValueRatio"/>
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    <link:label id="lab_nmih_EligiblePoliciesPoolNineMember_713a1aaf-164c-4bf4-8655-d2e1e3df2447_terseLabel_en-US" xlink:label="lab_nmih_EligiblePoliciesPoolNineMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Risk written policies in 2023</link:label>
    <link:label id="lab_nmih_EligiblePoliciesPoolNineMember_label_en-US" xlink:label="lab_nmih_EligiblePoliciesPoolNineMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Eligible Policies, Pool Nine [Member]</link:label>
    <link:label id="lab_nmih_EligiblePoliciesPoolNineMember_documentation_en-US" xlink:label="lab_nmih_EligiblePoliciesPoolNineMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Eligible Policies, Pool Nine</link:label>
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    <link:label id="lab_nmih_PriorYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported_c6fdf202-47b4-4caf-9c9f-78a81d4a3fc8_terseLabel_en-US" xlink:label="lab_nmih_PriorYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prior year, IBNR</link:label>
    <link:label id="lab_nmih_PriorYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported_label_en-US" xlink:label="lab_nmih_PriorYearClaimsAndClaimsAdjustmentExpenseIncurredButNotReported" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prior Year Claims and Claims Adjustment Expense, Incurred but Not Reported</link:label>
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    <link:label id="lab_us-gaap_DirectPremiumsEarned_6933b778-00c0-4577-aab5-e6e28d45e8ac_terseLabel_en-US" xlink:label="lab_us-gaap_DirectPremiumsEarned" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Direct</link:label>
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    <link:label id="lab_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_121146b1-9947-495d-83be-bb37a014de76_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Weighted-average remaining lease term (in years)</link:label>
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    <link:label id="lab_dei_EntityFileNumber_c29d2cca-1e8c-47be-aefb-9c1128ad5520_terseLabel_en-US" xlink:label="lab_dei_EntityFileNumber" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity File Number</link:label>
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    <link:label id="lab_us-gaap_DebtInstrumentRedemptionPricePercentage_b4812c6b-e9ad-400c-b898-4312600aaaca_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentRedemptionPricePercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Redemption price (in percent)</link:label>
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    <link:label id="lab_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_8713be6c-d4cc-4a20-a51b-e54bdb55151b_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Roll-forward of Level 3 liabilities:</link:label>
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    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_b980fdae-4f23-48b6-a5f0-df0fa5b095c4_terseLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Schedule of fair values and gross unrealized gains and losses</link:label>
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    <link:label id="lab_us-gaap_USTreasuryAndGovernmentMember_aae9206e-cad8-496e-8e62-a1af402ed576_netLabel_en-US" xlink:label="lab_us-gaap_USTreasuryAndGovernmentMember" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">U.S. Treasury securities and obligations of U.S. government agencies</link:label>
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    <link:label id="lab_us-gaap_USTreasuryAndGovernmentMember_label_en-US" xlink:label="lab_us-gaap_USTreasuryAndGovernmentMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">US Treasury and Government [Member]</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_957ab449-77d9-4003-8795-72cb5769ed68_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2025</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
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    <link:label id="lab_nmih_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseClaimsAppliedtoDeductible_41dfd16d-2c95-4248-8899-8b0ff1c0ad39_terseLabel_en-US" xlink:label="lab_nmih_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseClaimsAppliedtoDeductible" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Claims applied to pool deductible</link:label>
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    <link:label id="lab_us-gaap_InvestmentIncomeInterestAndDividend_bed9e0f9-c567-4a8c-9d97-33b102b2543b_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentIncomeInterestAndDividend" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Investment income</link:label>
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    <link:label id="lab_us-gaap_OperatingLeasePayments_ab23937d-f0b5-44e1-9b10-03d28f127f2f_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasePayments" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Cash paid on operating leases</link:label>
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    <link:label id="lab_us-gaap_ReinsuranceRecoverablesGross_ed15ca45-f79f-4205-a8d1-2a1f0f507aba_terseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRecoverablesGross" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance recoverable</link:label>
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    <link:label id="lab_us-gaap_SecuredDebt_99d22878-2c68-4930-81bb-4e99d1cbe5b5_terseLabel_en-US" xlink:label="lab_us-gaap_SecuredDebt" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt</link:label>
    <link:label id="lab_us-gaap_SecuredDebt_label_en-US" xlink:label="lab_us-gaap_SecuredDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Secured Debt</link:label>
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    <link:label id="lab_us-gaap_IncreaseDecreaseInUnearnedPremiums_edec7a34-f6e1-4ce0-b85b-c5d0f8809194_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInUnearnedPremiums" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Unearned premiums</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInUnearnedPremiums_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInUnearnedPremiums" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Increase (Decrease) in Unearned Premiums</link:label>
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    <link:label id="lab_us-gaap_StatutoryAccountingPracticesLineItems_e174f0a0-c4cd-4154-901a-f972fe0d8003_terseLabel_en-US" xlink:label="lab_us-gaap_StatutoryAccountingPracticesLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Statutory Accounting Practices [Line Items]</link:label>
    <link:label id="lab_us-gaap_StatutoryAccountingPracticesLineItems_label_en-US" xlink:label="lab_us-gaap_StatutoryAccountingPracticesLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Statutory Accounting Practices [Line Items]</link:label>
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    <link:label id="lab_nmih_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseClaimsPaidIncludingAmountsCoveredByInsurance_e3804974-b1c4-4c73-8081-2e546705dfec_terseLabel_en-US" xlink:label="lab_nmih_LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseClaimsPaidIncludingAmountsCoveredByInsurance" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Claims paid, including amounts covered by insurance</link:label>
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    <link:label id="lab_nmih_A2022QSRTransactionMember_documentation_en-US" xlink:label="lab_nmih_A2022QSRTransactionMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2022 QSR Transaction</link:label>
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    <link:label id="lab_us-gaap_StatutoryAccountingPracticesStatutoryNetIncomeAmount_209ad60a-66d0-4ff4-8778-d077cf22ccda_terseLabel_en-US" xlink:label="lab_us-gaap_StatutoryAccountingPracticesStatutoryNetIncomeAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net income amount</link:label>
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    <link:label id="lab_us-gaap_LongTermDebt_4036905e-0f88-4128-8ff0-1bfa7461b323_verboseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebt" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Carried cost</link:label>
    <link:label id="lab_us-gaap_LongTermDebt_label_en-US" xlink:label="lab_us-gaap_LongTermDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Long-term Debt</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebt" xlink:to="lab_us-gaap_LongTermDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_AssetsFairValueDisclosure_37522bfa-9686-46ef-8f3a-a907bf30f6f6_totalLabel_en-US" xlink:label="lab_us-gaap_AssetsFairValueDisclosure" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total assets</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AssetsFairValueDisclosure" xlink:to="lab_us-gaap_AssetsFairValueDisclosure" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PrepaidExpenseCurrentAndNoncurrent_4a6fabe5-934a-4ea9-821a-940fde2fbba6_terseLabel_en-US" xlink:label="lab_us-gaap_PrepaidExpenseCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prepaid expenses</link:label>
    <link:label id="lab_us-gaap_PrepaidExpenseCurrentAndNoncurrent_label_en-US" xlink:label="lab_us-gaap_PrepaidExpenseCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prepaid Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpenseCurrentAndNoncurrent"/>
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    <link:label id="lab_us-gaap_CededCreditRiskLineItems_8bf3217b-acc3-40b4-8abf-e015ed59e5e7_terseLabel_en-US" xlink:label="lab_us-gaap_CededCreditRiskLineItems" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Ceded Credit Risk [Line Items]</link:label>
    <link:label id="lab_us-gaap_CededCreditRiskLineItems_label_en-US" xlink:label="lab_us-gaap_CededCreditRiskLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Ceded Credit Risk [Line Items]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskLineItems" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CededCreditRiskLineItems"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CededCreditRiskLineItems" xlink:to="lab_us-gaap_CededCreditRiskLineItems" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueInputsLevel1Member_7166ee5a-a2ce-41f7-8ea0-7e29f825f678_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel1Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Quoted Prices in Active Markets for Identical Assets (Level 1)</link:label>
    <link:label id="lab_us-gaap_FairValueInputsLevel1Member_label_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel1Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value, Inputs, Level 1 [Member]</link:label>
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    <link:label id="lab_us-gaap_OtherLiabilities_label_en-US" xlink:label="lab_us-gaap_OtherLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Other Liabilities</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilities"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherLiabilities" xlink:to="lab_us-gaap_OtherLiabilities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DirectPremiumsWritten_1a7cb6ff-c25b-49d9-8273-90ae12c0ea6a_terseLabel_en-US" xlink:label="lab_us-gaap_DirectPremiumsWritten" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Direct</link:label>
    <link:label id="lab_us-gaap_DirectPremiumsWritten_label_en-US" xlink:label="lab_us-gaap_DirectPremiumsWritten" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Direct Premiums Written</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DirectPremiumsWritten" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DirectPremiumsWritten"/>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_286c81b8-c0d3-4643-999d-c523001af290_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2027</link:label>
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    <link:label id="lab_us-gaap_LesseeLeaseDescriptionTable_0737837a-ec73-4928-b3e3-8d3fb71159b8_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeLeaseDescriptionTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Lessee, Lease, Description [Table]</link:label>
    <link:label id="lab_us-gaap_LesseeLeaseDescriptionTable_label_en-US" xlink:label="lab_us-gaap_LesseeLeaseDescriptionTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Lessee, Lease, Description [Table]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
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    <link:label id="lab_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock_fde39236-fbe0-4a4a-a469-7e7326592ea9_terseLabel_en-US" xlink:label="lab_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Organization, Basis of Presentation and Summary of Accounting Principles</link:label>
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    <link:label id="lab_nmih_SeniorSecuredTermLoan2018Member_8439fd3b-d19e-4da6-b811-ba6dbaea0318_terseLabel_en-US" xlink:label="lab_nmih_SeniorSecuredTermLoan2018Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2018 Term loan</link:label>
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    <link:label id="lab_us-gaap_EarningsPerShareTextBlock_6f75200a-63c3-4bd7-b4e1-2a0944cc4e7c_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerShareTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Earnings per Share (EPS)</link:label>
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    <link:label id="lab_us-gaap_TreasuryStockValueAcquiredCostMethod_a7e157c7-f623-4a23-b83c-81c67316898c_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Repurchase of common stock</link:label>
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    <link:label id="lab_us-gaap_TreasuryStockAcquiredAverageCostPerShare_c127e12f-1102-4c91-b248-fe3de23dae0a_terseLabel_en-US" xlink:label="lab_us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Shares repurchased, average price per share (in dollar per share)</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
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    <link:label id="lab_dei_EntityInteractiveDataCurrent_e46e678c-46e5-40a7-878a-22f2aa2d63ed_terseLabel_en-US" xlink:label="lab_dei_EntityInteractiveDataCurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity Interactive Data Current</link:label>
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    <link:label id="lab_nmih_StatutoryAccountingPracticesContingencyReserve_77e95ee6-64bf-42da-bf70-14dffa689e36_terseLabel_en-US" xlink:label="lab_nmih_StatutoryAccountingPracticesContingencyReserve" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Contingency reserve</link:label>
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    <link:label id="lab_nmih_StatutoryAccountingPracticesContingencyReserve_documentation_en-US" xlink:label="lab_nmih_StatutoryAccountingPracticesContingencyReserve" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Contingency reserve recorded under Statutory Accounting Principles is a liability to protect against loss during periods of extreme contraction.</link:label>
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    <link:label id="lab_us-gaap_StatutoryAccountingPracticesDisclosureTextBlock_3f6d9764-55cf-4e9b-b6b8-3254686c6187_terseLabel_en-US" xlink:label="lab_us-gaap_StatutoryAccountingPracticesDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Schedule of statutory net income (loss), surplus, contingency reserve and risk-to-capital ratio</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatutoryAccountingPracticesDisclosureTextBlock" xlink:to="lab_us-gaap_StatutoryAccountingPracticesDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_ReinsuranceAgreementOptionalTerminationRightPercentOfReinsuranceCoverageThreshold_f3256425-f460-4262-adb4-4dbfa2eb8aeb_terseLabel_en-US" xlink:label="lab_nmih_ReinsuranceAgreementOptionalTerminationRightPercentOfReinsuranceCoverageThreshold" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance coverage amount amortized (as a percent)</link:label>
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    <link:label id="lab_srt_MinimumMember_ab669dd8-23a4-4590-a155-7dec60840ebf_terseLabel_en-US" xlink:label="lab_srt_MinimumMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Minimum</link:label>
    <link:label id="lab_srt_MinimumMember_label_en-US" xlink:label="lab_srt_MinimumMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Minimum [Member]</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_srt_MinimumMember" xlink:to="lab_srt_MinimumMember" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleRealizedGain_3525a84d-0674-4dab-af04-be41648e856c_terseLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleRealizedGain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Gross realized investment gains</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_6f129f7a-afbc-4d23-8d45-e4f2707e25b5_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2024</link:label>
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    <link:label id="lab_us-gaap_LineOfCredit_8f2a4ca8-947e-48d1-b52f-594e78f10f95_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCredit" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Borrowings outstanding</link:label>
    <link:label id="lab_us-gaap_LineOfCredit_label_en-US" xlink:label="lab_us-gaap_LineOfCredit" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Long-term Line of Credit</link:label>
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    <link:label id="lab_us-gaap_LiabilitiesFairValueDisclosure_18599693-16e6-4a3a-b4f3-62b4743b147e_totalLabel_en-US" xlink:label="lab_us-gaap_LiabilitiesFairValueDisclosure" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total liabilities</link:label>
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    <link:label id="lab_us-gaap_UnearnedPremiums_42475e1e-aae2-4504-a35b-a97a3f5f0655_terseLabel_en-US" xlink:label="lab_us-gaap_UnearnedPremiums" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Unearned premiums</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnearnedPremiums" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UnearnedPremiums"/>
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    <link:label id="lab_us-gaap_DebtDisclosureTextBlock_3b15ce15-0c03-43e0-a5c4-cc642e47e90e_terseLabel_en-US" xlink:label="lab_us-gaap_DebtDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt</link:label>
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    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_c96046e9-6b5d-4c44-9729-dc91c483f039_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Due in one year or less</link:label>
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    <link:label id="lab_us-gaap_ReinsuranceTextBlock_1554e4f0-33c3-4d2a-b584-8483b507372e_terseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance</link:label>
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    <link:label id="lab_nmih_SecuredRevolvingCreditFacility2021Member_0e579c63-0a06-4682-9c2c-b744b1004df0_terseLabel_en-US" xlink:label="lab_nmih_SecuredRevolvingCreditFacility2021Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2021 Revolving credit facility</link:label>
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    <link:label id="lab_us-gaap_SubsequentEventTable_561127ee-d77e-42f9-8bcd-9b9e9e6b7a57_terseLabel_en-US" xlink:label="lab_us-gaap_SubsequentEventTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Subsequent Event [Table]</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeasesTextBlock_bd24f352-0a0b-400b-aa81-fbb1469fea58_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeasesTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Leases</link:label>
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    <link:label id="lab_nmih_AnticipatedOperatingExpensePaymentsAnnual_ade420ba-ba07-4ceb-96eb-bdac9f19cbe8_terseLabel_en-US" xlink:label="lab_nmih_AnticipatedOperatingExpensePaymentsAnnual" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Anticipated payment related to annual operating expenses</link:label>
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    <link:label id="lab_nmih_AnticipatedOperatingExpensePaymentsAnnual_documentation_en-US" xlink:label="lab_nmih_AnticipatedOperatingExpensePaymentsAnnual" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Amount of anticipated payments related to operating expenses of counterparty.</link:label>
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    <link:label id="lab_us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock_c1e74c1c-5ed3-4417-af41-57134b7821ee_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Investments</link:label>
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    <link:label id="lab_dei_LegalEntityAxis_480a4051-58ee-40e0-a2a7-74ea4ddcca29_terseLabel_en-US" xlink:label="lab_dei_LegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Legal Entity [Axis]</link:label>
    <link:label id="lab_dei_LegalEntityAxis_label_en-US" xlink:label="lab_dei_LegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Legal Entity [Axis]</link:label>
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    <link:label id="lab_dei_CoverAbstract_d1651fe0-d8fb-4e70-862d-8baa3fdf3591_terseLabel_en-US" xlink:label="lab_dei_CoverAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Cover page.</link:label>
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    <link:label id="lab_nmih_DebtSecuritiesCorporateComponentOfTotal.Percentage_b98ae735-fa80-4388-8aed-67c1f24d1e4e_terseLabel_en-US" xlink:label="lab_nmih_DebtSecuritiesCorporateComponentOfTotal.Percentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Corporate debt securities as component of total (percent)</link:label>
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    <link:label id="lab_nmih_DebtSecuritiesCorporateComponentOfTotal.Percentage_documentation_en-US" xlink:label="lab_nmih_DebtSecuritiesCorporateComponentOfTotal.Percentage" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities, Corporate, Component Of Total. Percentage</link:label>
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    <link:label id="lab_us-gaap_CostsAndExpenses_168d13e8-09bb-4eb7-b627-004fd12b5a9a_totalLabel_en-US" xlink:label="lab_us-gaap_CostsAndExpenses" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total expenses</link:label>
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    <link:label id="lab_us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured_5f751569-53db-41f5-9b57-97df262dbda5_terseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Amount reinsured</link:label>
    <link:label id="lab_us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured_label_en-US" xlink:label="lab_us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention Policy, Excess Retention, Amount Reinsured</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ReinsuranceRetentionPolicyExcessRetentionAmountReinsured"/>
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    <link:label id="lab_nmih_ILNTransactionsMember_b9f9cd82-ff23-44cb-b7ea-c37476ce9f0e_terseLabel_en-US" xlink:label="lab_nmih_ILNTransactionsMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">ILN transactions</link:label>
    <link:label id="lab_nmih_ILNTransactionsMember_label_en-US" xlink:label="lab_nmih_ILNTransactionsMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">ILN Transactions [Member]</link:label>
    <link:label id="lab_nmih_ILNTransactionsMember_documentation_en-US" xlink:label="lab_nmih_ILNTransactionsMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">ILN Transactions [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_ILNTransactionsMember" xlink:href="nmih-20220331.xsd#nmih_ILNTransactionsMember"/>
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    <link:label id="lab_us-gaap_ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock_dfceeb14-8e29-4153-89c6-158308978c23_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Schedule of aging unrealized losses</link:label>
    <link:label id="lab_us-gaap_ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock_label_en-US" xlink:label="lab_us-gaap_ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Schedule of Unrealized Loss on Investments [Table Text Block]</link:label>
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    <link:label id="lab_us-gaap_ClassOfWarrantOrRightOutstanding_d0279e33-6e36-46e4-8321-2f0ff205a1e6_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Class of warrant or right, outstanding (in shares)</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_9cd6b75d-d0c7-4bdd-bf7a-e3ab4f0c8315_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Less effects of discounting</link:label>
    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_label_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
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    <link:label id="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses_2b0825b5-cc23-4b6e-9b47-b3a6efc0cd70_terseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance recoverable on unpaid claims</link:label>
    <link:label id="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses_72c3de0c-8df7-4358-881e-864877a636aa_periodStartLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Less reinsurance recoverables</link:label>
    <link:label id="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses_7dd99b2c-6f97-4b1b-8037-d0d9d65e3c90_periodEndLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Add reinsurance recoverables</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses" xlink:to="lab_us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet_b5e3f40b-0057-4741-be23-91316336a2f3_periodStartLabel_en-US" xlink:label="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Beginning balance, net of reinsurance recoverables</link:label>
    <link:label id="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet_5f6aa854-207e-4e50-b006-c8234a9d2899_periodEndLabel_en-US" xlink:label="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reserve at end of period, net of reinsurance recoverables</link:label>
    <link:label id="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet_label_en-US" xlink:label="lab_us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Unpaid Claims and Claims Adjustment Expense, Net</link:label>
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    <link:label id="lab_nmih_LineofCreditandRelatedWarrantsTextBlock_fd7f5279-606a-4657-b9fe-359437295941_terseLabel_en-US" xlink:label="lab_nmih_LineofCreditandRelatedWarrantsTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrants</link:label>
    <link:label id="lab_nmih_LineofCreditandRelatedWarrantsTextBlock_label_en-US" xlink:label="lab_nmih_LineofCreditandRelatedWarrantsTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Line of Credit and Related Warrants [Text Block]</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_nmih_LineofCreditandRelatedWarrantsTextBlock" xlink:href="nmih-20220331.xsd#nmih_LineofCreditandRelatedWarrantsTextBlock"/>
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    <link:label id="lab_us-gaap_PremiumsWrittenNetConsolidatedAbstract_e6045b55-9e7b-4cc3-ba4c-0b0d7e51060a_terseLabel_en-US" xlink:label="lab_us-gaap_PremiumsWrittenNetConsolidatedAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net premiums written</link:label>
    <link:label id="lab_us-gaap_PremiumsWrittenNetConsolidatedAbstract_label_en-US" xlink:label="lab_us-gaap_PremiumsWrittenNetConsolidatedAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Premiums Written, Net [Abstract]</link:label>
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    <link:label id="lab_us-gaap_AdditionalPaidInCapitalMember_40df23c8-5d1b-43ed-a1a5-ed05ce26b41c_terseLabel_en-US" xlink:label="lab_us-gaap_AdditionalPaidInCapitalMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Additional Paid-in Capital</link:label>
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    <link:label id="lab_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured_label_en-US" xlink:label="lab_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention Policy, Excess Retention, Second Layer Amount Reinsured</link:label>
    <link:label id="lab_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured_documentation_en-US" xlink:label="lab_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention Policy, Excess Retention, Second Layer Amount Reinsured</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured" xlink:href="nmih-20220331.xsd#nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured" xlink:to="lab_nmih_ReinsuranceRetentionPolicyExcessRetentionSecondLayerAmountReinsured" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_NumberOfSharesRightToPurchasePerWarrant_6d817c17-5e8e-421b-964e-7787c8ccd32c_terseLabel_en-US" xlink:label="lab_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Right to purchase, number of shares per warrant (in shares)</link:label>
    <link:label id="lab_nmih_NumberOfSharesRightToPurchasePerWarrant_label_en-US" xlink:label="lab_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Number Of Shares, Right To Purchase Per Warrant</link:label>
    <link:label id="lab_nmih_NumberOfSharesRightToPurchasePerWarrant_documentation_en-US" xlink:label="lab_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Number Of Shares, Right To Purchase Per Warrant</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:href="nmih-20220331.xsd#nmih_NumberOfSharesRightToPurchasePerWarrant"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:to="lab_nmih_NumberOfSharesRightToPurchasePerWarrant" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongtermDebtTypeDomain_83a5ad4f-6dfb-4226-87ff-c6398367c2a7_terseLabel_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Long-term Debt, Type [Domain]</link:label>
    <link:label id="lab_us-gaap_LongtermDebtTypeDomain_label_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Long-term Debt, Type [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongtermDebtTypeDomain" xlink:to="lab_us-gaap_LongtermDebtTypeDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_MortgagePoolInsuranceClaimDeductible_089e563b-16ce-430c-beb5-d1aaa4d30d6f_terseLabel_en-US" xlink:label="lab_nmih_MortgagePoolInsuranceClaimDeductible" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Deductible on policy</link:label>
    <link:label id="lab_nmih_MortgagePoolInsuranceClaimDeductible_label_en-US" xlink:label="lab_nmih_MortgagePoolInsuranceClaimDeductible" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Mortgage Pool Insurance, Claim Deductible</link:label>
    <link:label id="lab_nmih_MortgagePoolInsuranceClaimDeductible_documentation_en-US" xlink:label="lab_nmih_MortgagePoolInsuranceClaimDeductible" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Mortgage Pool Insurance, Claim Deductible</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_MortgagePoolInsuranceClaimDeductible" xlink:href="nmih-20220331.xsd#nmih_MortgagePoolInsuranceClaimDeductible"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_MortgagePoolInsuranceClaimDeductible" xlink:to="lab_nmih_MortgagePoolInsuranceClaimDeductible" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_InterestPayableCurrentAndNoncurrent_83652bc6-02b4-491b-9d99-08241bcbeb8a_terseLabel_en-US" xlink:label="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Interest payable</link:label>
    <link:label id="lab_us-gaap_InterestPayableCurrentAndNoncurrent_label_en-US" xlink:label="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Interest Payable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:to="lab_us-gaap_InterestPayableCurrentAndNoncurrent" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock_2b9f341a-62d7-40bc-b4c3-f8e6d3b4441e_terseLabel_en-US" xlink:label="lab_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reserves for Insurance Claims and Claim Expenses</link:label>
    <link:label id="lab_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock_label_en-US" xlink:label="lab_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock" xlink:to="lab_us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce_32581d62-0a95-45d4-9683-c116fd45e264_terseLabel_en-US" xlink:label="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Risk-in-Force of loans in pool past due 60 days or more</link:label>
    <link:label id="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce_label_en-US" xlink:label="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Loans In Pool, Past Due 60 Days Or More, Loan Risk in Force</link:label>
    <link:label id="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce_documentation_en-US" xlink:label="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Loans In Pool, Past Due 60 Days Or More, Risk in Force</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:href="nmih-20220331.xsd#nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:to="lab_nmih_LoansInPoolPastDue60DaysOrMoreLoanRiskinForce" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_65807b42-8281-4221-b287-1884e83a7059_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Purchase of fixed-maturity investments, available-for-sale</link:label>
    <link:label id="lab_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_label_en-US" xlink:label="lab_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Payments to Acquire Debt Securities, Available-for-sale</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:to="lab_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_PriorToMarch12025Member_a3a06cbc-321e-46d0-a255-78388bdf117c_terseLabel_en-US" xlink:label="lab_nmih_PriorToMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prior to March 1, 2025</link:label>
    <link:label id="lab_nmih_PriorToMarch12025Member_label_en-US" xlink:label="lab_nmih_PriorToMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prior To March 1, 2025 [Member]</link:label>
    <link:label id="lab_nmih_PriorToMarch12025Member_documentation_en-US" xlink:label="lab_nmih_PriorToMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Prior To March 1, 2025</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_PriorToMarch12025Member" xlink:href="nmih-20220331.xsd#nmih_PriorToMarch12025Member"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_PriorToMarch12025Member" xlink:to="lab_nmih_PriorToMarch12025Member" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage_c9095a30-67e5-46a0-9586-a999090ac87f_terseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Percent of premiums ceded under QSR Transaction</link:label>
    <link:label id="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage_fc0b1393-4762-42a8-a33a-560049f1578f_verboseLabel_en-US" xlink:label="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Percent of pool RIF reinsured</link:label>
    <link:label id="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage_label_en-US" xlink:label="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention Policy, Reinsured Risk, Percentage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:to="lab_us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_491a69b0-1780-43cb-b046-edfd37894334_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrants issued (in shares)</link:label>
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_label_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:to="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid_785968f5-2dee-40e8-9626-8a2a2c17384a_terseLabel_en-US" xlink:label="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Risk premiums paid</link:label>
    <link:label id="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid_label_en-US" xlink:label="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention, Risk Premiums Paid</link:label>
    <link:label id="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid_documentation_en-US" xlink:label="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance Retention, Risk Premiums Paid</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:href="nmih-20220331.xsd#nmih_ReinsuranceRetentionRiskPremiumsPaid"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:to="lab_nmih_ReinsuranceRetentionRiskPremiumsPaid" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve_4ad35e53-a6ea-4965-855b-e17a03a5a808_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reserve for insurance claims and claim expenses</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve" xlink:to="lab_us-gaap_IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod_dee34f5a-42e1-4bcd-8ff6-7487187286ae_terseLabel_en-US" xlink:label="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrants expired unexercised resulting in gain (loss) during period</link:label>
    <link:label id="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod_label_en-US" xlink:label="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Class Of Warrant Or Right, Warrants Expired Unexercised Resulting In Gain (Loss) During Period</link:label>
    <link:label id="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod_documentation_en-US" xlink:label="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Class Of Warrant Or Right, Warrants Expired Unexercised Resulting In Gain (Loss) During Period</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:href="nmih-20220331.xsd#nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:to="lab_nmih_ClassOfWarrantOrRightWarrantsExpiredUnexercisedResultingInGainLossDuringPeriod" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_LongTermDebtFairValue_224bb712-7067-48cb-9b05-40958260fe8e_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebtFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair value of long term debt</link:label>
    <link:label id="lab_us-gaap_LongTermDebtFairValue_label_en-US" xlink:label="lab_us-gaap_LongTermDebtFairValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Long-term Debt, Fair Value</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebtFairValue" xlink:to="lab_us-gaap_LongTermDebtFairValue" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_e0f31110-c689-46e2-8b99-dcba59086341_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Software and equipment</link:label>
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    <link:label id="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_d6c89e28-ef24-4661-9632-035d28d44571_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Cash flows from financing activities</link:label>
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    <link:label id="lab_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_540faf41-5250-4c03-b143-6b797987ec58_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Accounts payable and accrued expenses</link:label>
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    <link:label id="lab_us-gaap_CededPremiumsEarned_72a56707-63d5-4187-81fc-59319900774d_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_CededPremiumsEarned" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Ceded</link:label>
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    <link:label id="lab_nmih_SecuredRevolvingCreditFacility2018Member_c1120a41-2dd0-484b-867e-5d8110289636_terseLabel_en-US" xlink:label="lab_nmih_SecuredRevolvingCreditFacility2018Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2018 Revolving credit facility</link:label>
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    <link:label id="lab_nmih_PremiumsEarnedPercentOfRisk_e166982f-6b34-4105-b372-8b51862dabc5_terseLabel_en-US" xlink:label="lab_nmih_PremiumsEarnedPercentOfRisk" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Percent of premiums earned under 2018 QSR Transaction</link:label>
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    <link:label id="lab_us-gaap_MeasurementInputExpectedTermMember_228184dd-709f-440d-b586-3fa4e7faa6b8_verboseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputExpectedTermMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Expected life</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputExpectedTermMember"/>
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    <link:label id="lab_dei_EntityAddressCityOrTown_7ad8b709-0464-44e9-880c-63ddd9410f15_terseLabel_en-US" xlink:label="lab_dei_EntityAddressCityOrTown" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity Address, City or Town</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressCityOrTown"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_dei_EntityAddressCityOrTown" xlink:to="lab_dei_EntityAddressCityOrTown" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss_f6ce5a6a-c706-4771-b2da-94a5389c650d_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Gross realized investment losses</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss" xlink:to="lab_us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsForRepurchaseOfCommonStock_81aa1b63-250b-418b-9908-e7ee3376c132_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Repurchases of common stock</link:label>
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    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_4178c059-a85b-4037-b1ed-9bb80279e7e2_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value</link:label>
    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_label_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract"/>
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    <link:label id="lab_us-gaap_StockholdersEquityAbstract_92499b04-7528-447f-9a19-8d904c7a3a12_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Shareholders' equity</link:label>
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    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_0cbb6984-3627-49b4-86ba-a383b1a2222c_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Due after one through five years</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue"/>
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    <link:label id="lab_us-gaap_InvestmentIncomeNet_c6cf3cc7-9e23-4053-9d18-b6a9015e153c_totalLabel_en-US" xlink:label="lab_us-gaap_InvestmentIncomeNet" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Net investment income</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
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    <link:label id="lab_us-gaap_DebtInstrumentFaceAmount_c8750765-6cdc-4ca4-9422-10300cfc2227_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentFaceAmount" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt instrument face amount</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
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    <link:label id="lab_us-gaap_InterestExpense_666ea102-17f1-41dd-b48c-3d822568cb8a_terseLabel_en-US" xlink:label="lab_us-gaap_InterestExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Interest expense</link:label>
    <link:label id="lab_us-gaap_InterestExpense_label_en-US" xlink:label="lab_us-gaap_InterestExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Interest Expense</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_c7ff5a79-121e-4e99-940e-2395238d8137_totalLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total undiscounted lease payments</link:label>
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    <link:label id="lab_nmih_ThirdPartyReinsurersMember_b3e2b274-a3f5-4f96-9e06-c4a4ef1b4828_terseLabel_en-US" xlink:label="lab_nmih_ThirdPartyReinsurersMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Third-party reinsurers</link:label>
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    <link:label id="lab_nmih_ClassofWarrantorRightNumberofWarrantsExercisedDuringPeriod_d3a42715-2c21-4439-808c-c0fa38c2674c_terseLabel_en-US" xlink:label="lab_nmih_ClassofWarrantorRightNumberofWarrantsExercisedDuringPeriod" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrants exercised (in shares)</link:label>
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    <link:label id="lab_us-gaap_DeferredFinanceCostsGross_eeaa7eb1-4a63-413b-b2a6-34529109b518_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredFinanceCostsGross" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt issuance costs</link:label>
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    <link:label id="lab_us-gaap_StockholdersEquityPolicyTextBlock_b1148238-30a0-49a7-885a-c13d847276ff_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityPolicyTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Share Repurchases</link:label>
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    <link:label id="lab_us-gaap_OtherIncome_71cd061f-6a59-4d24-942c-1fe6a02d1986_terseLabel_en-US" xlink:label="lab_us-gaap_OtherIncome" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Other revenues</link:label>
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    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtSecurities_0f03f444-c284-4c50-b2b4-0b14442ace34_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fixed maturities, available-for-sale, at fair value (amortized cost of $2,111,869 and $2,078,773 as of March 31, 2022 and December 31, 2021, respectively)</link:label>
    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesDebtSecurities_209b23e2-2b00-455e-8717-2b738079f3b1_verboseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value</link:label>
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    <link:label id="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_b67deea8-1820-4187-a978-e1c64124d4ec_terseLabel_en-US" xlink:label="lab_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2026</link:label>
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    <link:label id="lab_nmih_ReinsuranceRetentionPolicyTermOfUnderlyingMortgageAmortization_a0d6c880-b8a7-4d3c-89cf-247b67f5155a_terseLabel_en-US" xlink:label="lab_nmih_ReinsuranceRetentionPolicyTermOfUnderlyingMortgageAmortization" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reinsurance coverage, term of underlying mortgage amortization (in years)</link:label>
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    <link:label id="lab_us-gaap_DebtDisclosureAbstract_c4eaa9d6-a1de-4de5-bcc9-4e4944d9fa10_terseLabel_en-US" xlink:label="lab_us-gaap_DebtDisclosureAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Disclosure [Abstract]</link:label>
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    <link:label id="lab_nmih_WarrantLiability_30ea9037-f411-4e6a-91ed-f256708ae74a_verboseLabel_en-US" xlink:label="lab_nmih_WarrantLiability" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrant liability</link:label>
    <link:label id="lab_nmih_WarrantLiability_label_en-US" xlink:label="lab_nmih_WarrantLiability" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrant Liability</link:label>
    <link:label id="lab_nmih_WarrantLiability_documentation_en-US" xlink:label="lab_nmih_WarrantLiability" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrant Liability</link:label>
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    <link:label id="lab_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_84a25b88-5dc4-417a-904e-79688fccc047_totalLabel_en-US" xlink:label="lab_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Income before income taxes</link:label>
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    <link:label id="lab_us-gaap_FairValueInputsLevel2Member_68ad3bcd-b2ae-418e-b075-d561627fc405_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueInputsLevel2Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Significant Other Observable Inputs (Level 2)</link:label>
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    <link:label id="lab_nmih_AfterMarch12025Member_0131b4d0-056e-4d36-a068-c84bb0839b1a_terseLabel_en-US" xlink:label="lab_nmih_AfterMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">After March 1, 2025</link:label>
    <link:label id="lab_nmih_AfterMarch12025Member_label_en-US" xlink:label="lab_nmih_AfterMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">After March 1, 2025 [Member]</link:label>
    <link:label id="lab_nmih_AfterMarch12025Member_documentation_en-US" xlink:label="lab_nmih_AfterMarch12025Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">After March 1, 2025</link:label>
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    <link:label id="lab_us-gaap_MeasurementInputExpectedDividendRateMember_64d4f0f5-c937-4aea-819a-d498d6f289a0_terseLabel_en-US" xlink:label="lab_us-gaap_MeasurementInputExpectedDividendRateMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Dividend yield</link:label>
    <link:label id="lab_us-gaap_MeasurementInputExpectedDividendRateMember_label_en-US" xlink:label="lab_us-gaap_MeasurementInputExpectedDividendRateMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Measurement Input, Expected Dividend Rate [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedDividendRateMember" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputExpectedDividendRateMember"/>
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    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_f9faeb54-6d1c-4959-8e4a-97b5131c4885_totalLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Fair Value</link:label>
    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_label_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities, Available-for-sale, Unrealized Loss Position</link:label>
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    <link:label id="lab_nmih_TwoThousandSeventeenILNTransactionMember_b6197ee9-78f9-4b79-9e5b-89a4500bfb38_terseLabel_en-US" xlink:label="lab_nmih_TwoThousandSeventeenILNTransactionMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2017 ILN transaction</link:label>
    <link:label id="lab_nmih_TwoThousandSeventeenILNTransactionMember_label_en-US" xlink:label="lab_nmih_TwoThousandSeventeenILNTransactionMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Two Thousand Seventeen ILN Transaction [Member]</link:label>
    <link:label id="lab_nmih_TwoThousandSeventeenILNTransactionMember_documentation_en-US" xlink:label="lab_nmih_TwoThousandSeventeenILNTransactionMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Two Thousand Seventeen ILN Transaction [Member]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_TwoThousandSeventeenILNTransactionMember" xlink:href="nmih-20220331.xsd#nmih_TwoThousandSeventeenILNTransactionMember"/>
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    <link:label id="lab_nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable_d8406751-4487-4ebd-b08a-fa59706d2ca5_terseLabel_en-US" xlink:label="lab_nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Percent of aggregate balance redeemable with equity offerings</link:label>
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    <link:label id="lab_nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable_documentation_en-US" xlink:label="lab_nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Instrument, Redemption Price, Percentage Of Principal Amount, Redeemable</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable" xlink:href="nmih-20220331.xsd#nmih_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemable"/>
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    <link:label id="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_b8726bf7-843e-4d41-932d-4c6f52aa12d1_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt securities, amortized cost</link:label>
    <link:label id="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_699b7fa9-4cef-46e8-af5d-f555b54ff11f_totalLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Amortized Cost</link:label>
    <link:label id="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_label_en-US" xlink:label="lab_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities, Available-for-sale, Amortized Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
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    <link:label id="lab_us-gaap_PaymentsToAcquireShortTermInvestments_d99c3c13-b9ca-4082-8fdd-1d8fb98ab1e9_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsToAcquireShortTermInvestments" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Purchase of short-term investments</link:label>
    <link:label id="lab_us-gaap_PaymentsToAcquireShortTermInvestments_label_en-US" xlink:label="lab_us-gaap_PaymentsToAcquireShortTermInvestments" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Payments to Acquire Short-term Investments</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsToAcquireShortTermInvestments" xlink:to="lab_us-gaap_PaymentsToAcquireShortTermInvestments" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_TwoThousandEighteenILNTransactionMember_3d971a8d-27ad-4cc1-9542-7f26bee3d2c3_terseLabel_en-US" xlink:label="lab_nmih_TwoThousandEighteenILNTransactionMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">2018 ILN transaction</link:label>
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    <link:label id="lab_us-gaap_CorporateDebtSecuritiesMember_e6300096-b4f9-4e61-8198-2c79e3922447_verboseLabel_en-US" xlink:label="lab_us-gaap_CorporateDebtSecuritiesMember" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Corporate debt securities</link:label>
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    <link:label id="lab_us-gaap_AccumulatedOtherComprehensiveIncomeMember_5912750b-5912-4f2a-91ae-95bf61a59c52_terseLabel_en-US" xlink:label="lab_us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Accumulated Other Comprehensive Income</link:label>
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    <link:label id="lab_us-gaap_OtherAssets_0ec57423-82e4-4e07-86be-5cdcc6217e08_terseLabel_en-US" xlink:label="lab_us-gaap_OtherAssets" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Other assets</link:label>
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    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentNet_0bcdc162-6a41-4082-91d5-d3f387e03de9_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Software and equipment, net</link:label>
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    <link:label id="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_1330abc6-cacc-40ee-95e9-d2e84fe55ce9_totalLabel_en-US" xlink:label="lab_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Number of securities, total</link:label>
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    <link:label id="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpenseTable_label_en-US" xlink:label="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpenseTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Claims and Claims Adjustment Expense [Table]</link:label>
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    <link:label id="lab_nmih_DebtInstrumentCovenantTermsApplicablePremium_e92fe5f9-d9ea-4642-9eb1-17c4419805da_terseLabel_en-US" xlink:label="lab_nmih_DebtInstrumentCovenantTermsApplicablePremium" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Applicable premium</link:label>
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    <link:label id="lab_us-gaap_CommonStockParOrStatedValuePerShare_2f397474-e3a5-4abb-a96a-de75525f04cf_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Common stock, par value (in dollars per share)</link:label>
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    <link:label id="lab_us-gaap_LeasesAbstract_e2c4b2fc-4131-4817-a570-29146a395f0a_terseLabel_en-US" xlink:label="lab_us-gaap_LeasesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Leases [Abstract]</link:label>
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    <link:label id="lab_us-gaap_CashAndCashEquivalentsFairValueDisclosure_24ae62d7-7f17-463a-bb3a-56f3345d59df_terseLabel_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Cash, cash equivalents and short-term investments</link:label>
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    <link:label id="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense_28f37387-be7c-422e-a8fe-8705401b63fc_verboseLabel_en-US" xlink:label="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reserve for insurance claims and claim expenses</link:label>
    <link:label id="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense_17750570-bc61-43fb-84a7-9f5ae5328eef_terseLabel_en-US" xlink:label="lab_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total gross liability for unpaid claims and claim adjustment expenses</link:label>
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    <link:label id="lab_dei_EntityAddressPostalZipCode_d5bb38b4-a178-48bc-b1af-fee89667c0b7_terseLabel_en-US" xlink:label="lab_dei_EntityAddressPostalZipCode" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity Address, Postal Zip Code</link:label>
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    <link:label id="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_875b7139-50a3-4563-9eaa-1d984bb080a8_terseLabel_en-US" xlink:label="lab_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Diluted (in shares)</link:label>
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    <link:label id="lab_us-gaap_WarrantsAndRightsOutstanding_cea87796-b165-4d92-935e-c72c7e44afda_terseLabel_en-US" xlink:label="lab_us-gaap_WarrantsAndRightsOutstanding" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Warrant liability, at fair value</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="lab_us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet_b72517a9-8f62-4ab2-907e-11f2ffd58b5d_terseLabel_en-US" xlink:label="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Remaining deferred issuance costs, net of accumulated amortization</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:to="lab_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b86ccf24-971a-458d-ad16-8e8b7fd51c65_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Cash flows from operating activities</link:label>
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    <link:label id="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense_36139d12-e60f-4497-958b-10f1a620c0a1_terseLabel_en-US" xlink:label="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Reserve for prior year insurance claims and claim expenses</link:label>
    <link:label id="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense_label_en-US" xlink:label="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Prior Year Claims and Claims Adjustment Expense</link:label>
    <link:label id="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense_documentation_en-US" xlink:label="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Prior Year Claims and Claims Adjustment Expense</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:href="nmih-20220331.xsd#nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:to="lab_nmih_LiabilityforPriorYearClaimsandClaimsAdjustmentExpense" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_DebtSecuritiesByIndustryDomain_1f7d162e-ddc2-4245-a292-948614e0696e_terseLabel_en-US" xlink:label="lab_nmih_DebtSecuritiesByIndustryDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities By Industry [Domain]</link:label>
    <link:label id="lab_nmih_DebtSecuritiesByIndustryDomain_label_en-US" xlink:label="lab_nmih_DebtSecuritiesByIndustryDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Securities By Industry [Domain]</link:label>
    <link:label id="lab_nmih_DebtSecuritiesByIndustryDomain_documentation_en-US" xlink:label="lab_nmih_DebtSecuritiesByIndustryDomain" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">[Domain] for Debt Securities By Industry [Axis]</link:label>
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    <link:label id="lab_dei_EntityShellCompany_4fa5c2b2-cf03-4c45-bc26-87140b37ce7f_terseLabel_en-US" xlink:label="lab_dei_EntityShellCompany" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity Shell Company</link:label>
    <link:label id="lab_dei_EntityShellCompany_label_en-US" xlink:label="lab_dei_EntityShellCompany" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Entity Shell Company</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityShellCompany"/>
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    <link:label id="lab_us-gaap_DeferredPolicyAcquisitionCosts_b401ebe3-e432-4542-928a-7bc57fb3b03e_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredPolicyAcquisitionCosts" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Deferred policy acquisition costs, net</link:label>
    <link:label id="lab_us-gaap_DeferredPolicyAcquisitionCosts_label_en-US" xlink:label="lab_us-gaap_DeferredPolicyAcquisitionCosts" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Deferred Policy Acquisition Cost</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCosts" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredPolicyAcquisitionCosts"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DeferredPolicyAcquisitionCosts" xlink:to="lab_us-gaap_DeferredPolicyAcquisitionCosts" xlink:type="arc" order="1"/>
    <link:label id="lab_nmih_CurrentReinsuranceCoverage_2f9f0591-2eee-4722-b4de-e3f9ff532ddf_terseLabel_en-US" xlink:label="lab_nmih_CurrentReinsuranceCoverage" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Reinsurance Coverage</link:label>
    <link:label id="lab_nmih_CurrentReinsuranceCoverage_label_en-US" xlink:label="lab_nmih_CurrentReinsuranceCoverage" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Reinsurance Coverage</link:label>
    <link:label id="lab_nmih_CurrentReinsuranceCoverage_documentation_en-US" xlink:label="lab_nmih_CurrentReinsuranceCoverage" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Reinsurance Coverage</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_nmih_CurrentReinsuranceCoverage" xlink:href="nmih-20220331.xsd#nmih_CurrentReinsuranceCoverage"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nmih_CurrentReinsuranceCoverage" xlink:to="lab_nmih_CurrentReinsuranceCoverage" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_6eb71f49-6ddd-4dff-a3b6-57b8ed2b1be6_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Taxes paid related to net share settlement of equity awards</link:label>
    <link:label id="lab_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_label_en-US" xlink:label="lab_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Payment, Tax Withholding, Share-based Payment Arrangement</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
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    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_0325be4d-e6fd-4cee-8085-2e172170284c_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Credit facility borrowing capacity</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
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    <link:label id="lab_dei_CurrentFiscalYearEndDate_c943f438-7581-4be1-bbb1-392787828953_terseLabel_en-US" xlink:label="lab_dei_CurrentFiscalYearEndDate" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Fiscal Year End Date</link:label>
    <link:label id="lab_dei_CurrentFiscalYearEndDate_label_en-US" xlink:label="lab_dei_CurrentFiscalYearEndDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Current Fiscal Year End Date</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CurrentFiscalYearEndDate"/>
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    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_d34e2da6-8621-416a-ad16-cc92271be44d_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentNameDomain" xlink:to="lab_us-gaap_DebtInstrumentNameDomain" xlink:type="arc" order="1"/>
    <link:label id="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock_824da1b3-3ec3-40c4-9f26-743564716876_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Schedule of fair value measurements of financial instruments</link:label>
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    <link:label id="lab_nmih_PremiumReceivableNumberOfDaysToBeWrittenOff_63b2a110-1887-4d5a-a5d1-3a4b41ffe9de_terseLabel_en-US" xlink:label="lab_nmih_PremiumReceivableNumberOfDaysToBeWrittenOff" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Number of days to be written off</link:label>
    <link:label id="lab_nmih_PremiumReceivableNumberOfDaysToBeWrittenOff_label_en-US" xlink:label="lab_nmih_PremiumReceivableNumberOfDaysToBeWrittenOff" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Premium Receivable, Number of Days to be Written Off</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_nmih_PremiumReceivableNumberOfDaysToBeWrittenOff" xlink:href="nmih-20220331.xsd#nmih_PremiumReceivableNumberOfDaysToBeWrittenOff"/>
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    <link:label id="lab_us-gaap_StatementTable_c8a707e7-8344-4d87-974c-19c5458b3041_terseLabel_en-US" xlink:label="lab_us-gaap_StatementTable" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Statement [Table]</link:label>
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    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
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    <link:label id="lab_us-gaap_PaymentsForLossesAndLossAdjustmentExpense_0cdab23c-bd59-4311-b7c2-c5215307b43a_totalLabel_en-US" xlink:label="lab_us-gaap_PaymentsForLossesAndLossAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Total claims and claim expenses paid</link:label>
    <link:label id="lab_us-gaap_PaymentsForLossesAndLossAdjustmentExpense_label_en-US" xlink:label="lab_us-gaap_PaymentsForLossesAndLossAdjustmentExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:lang="en-US">Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForLossesAndLossAdjustmentExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsForLossesAndLossAdjustmentExpense"/>
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