<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-11-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001065332</issuerCik>
        <issuerName>NIC INC</issuerName>
        <issuerTradingSymbol>EGOV</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001455460</rptOwnerCik>
            <rptOwnerName>Knapp Robert W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>25501 WEST VALLEY PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>OLATHE</rptOwnerCity>
            <rptOwnerState>KS</rptOwnerState>
            <rptOwnerZipCode>66061</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Operating Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.9968</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>164135</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The transaction reported on this form is a program transaction under a Rule 10b5-1 plan for the Reporting Person, which concludes his 10b5-1 plan.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price.  These shares were sold in transactions at prices ranging from $19.89 to $20.13, inclusive.  The Reporting Person undertakes to provide to NIC Inc., any security holder of NIC Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges.</footnote>
        <footnote id="F3">The total shares have been increased by 2,344 shares to correct an error in reporting shares surrendered to NIC Inc. by the Reporting Person to satisfy tax withholding obligations on vesting of restricted shares.</footnote>
        <footnote id="F4">This total includes an additional 204 shares acquired pursuant to the NIC Inc. Employee Stock Purchase Plan since the last filing of a beneficial ownership report by the Reporting Person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Aimi Daughtery, Attorney-in-Fact for Robert W. Knapp</signatureName>
        <signatureDate>2015-11-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
