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

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-03-26</periodOfReport>

    <issuer>
        <issuerCik>0000879703</issuerCik>
        <issuerName>DIRECT INSITE CORP</issuerName>
        <issuerTradingSymbol>DIRI.OB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001197006</rptOwnerCik>
            <rptOwnerName>YUNICH PETER B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O METROPOLITAN VENTURE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>257 PARK AVENUE,SOUTH</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10010</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-03-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4167</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12959</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>2003A Stock Option Plan (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.26</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-07-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.26</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-03-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2006-04-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Series A Convertible Preferred Stock par value $0.0001</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.40</value>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>17587</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.00</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-09-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2005-09-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>175870</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>134410</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Indirect</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Payment for services as a Board member for the first quarter for fiscal year ending 12/31/03.</footnote>
        <footnote id="F2">The Reported number of shares of Common Stock underlying the Series A Convertible Preferred Stock reflects the initial conversion rate of 1-for-10 (the ratio of the current liquidation value of the Series A. Convertible Preferred Stock of $14.00 to the current conversion price of $1.40) pursuant to the terms of the Series A Convertible Preferred Stock.</footnote>
        <footnote id="F3">Metropolitan Venture Partners II, L.P. (&quot;MetVP&quot;) is the direct owner of an aggregate 134,680 shares of Series A Convertible Preferred Stock,par value $0.0001 per share,of Direct Insite Corp.(the &quot;Issuer&quot;),including shares acquired pursuant to the transaction pursuant to which Form 4 was filed 6/3/03,which are convertible as of the date of that statement into 1,346,800 shares of Common Stock,par value $0.0001 per share of the Issuer (the Shares&quot;).The Reporting Person is a Managing Partner of MetVP &amp; a limited partner of MetVP.In addition the Reporting Person is a limited partner in Metropolitan Venture Partners (Advisors) L.P. (&quot;MetVP Advisors&quot;) the general partner of MetVP &amp; is on the board &amp; is a shareholder in Metropolitan Ventures Corp.,the general partner of MetVP Advisors.As a result,the Reporting Person may be deemed to own beneficially &amp; indirectly the Shares.The Reporting Person disclaims beneficial ownership of the Shares except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peter B. Yunich</signatureName>
        <signatureDate>2004-03-26</signatureDate>
    </ownerSignature>
</ownershipDocument>

