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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-08-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001398659</issuerCik>
        <issuerName>Genpact LTD</issuerName>
        <issuerTradingSymbol>G</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001040508</rptOwnerCik>
            <rptOwnerName>BAIN CAPITAL INVESTORS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001520731</rptOwnerCik>
            <rptOwnerName>Bain Capital Partners Asia II, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001525871</rptOwnerCik>
            <rptOwnerName>Bain Capital Partners X, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561353</rptOwnerCik>
            <rptOwnerName>BCIP Associates IV, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561352</rptOwnerCik>
            <rptOwnerName>BCIP Associates IV-B, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561186</rptOwnerCik>
            <rptOwnerName>Glory Investments A Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561183</rptOwnerCik>
            <rptOwnerName>Glory Investments B Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561182</rptOwnerCik>
            <rptOwnerName>Glory Investments IV Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561181</rptOwnerCik>
            <rptOwnerName>Glory Investments IV-B Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2017-08-18</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8498874</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.72</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>49038390</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Bain Capital Investors, LLC (&quot;BCI&quot;) is the general partner of Bain Capital Partners Asia II, L.P. (&quot;Asia II&quot;). Asia II is the Class A shareholder of Glory Investments A Limited (&quot;Glory A&quot;). As a result, Asia II may be deemed to beneficially own Common Shares held by Glory A. Asia II disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. On August 18, 2017, Glory A sold 2,366,768 Common Shares. Following such sale, Glory A held 13,656,210 Common Shares.</footnote>
        <footnote id="F2">BCI is the general partner of Bain Capital Partners X, L.P. (&quot;BCP X&quot;). BCP X is the Class A shareholder of Glory Investments B Limited (&quot;Glory B&quot;). As a result, BCP X may be deemed to beneficially own Common Shares held by Glory B. BCP X disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. On August 18, 2017, Glory B sold 5,835,854 Common Shares. Following such sale, Glory B held 33,672,802 Common Shares.</footnote>
        <footnote id="F3">On August 18, 2017, Glory Investments IV Limited (&quot;Glory IV&quot;), whose Class A shareholder is BCIP Associates IV, L.P. (&quot;BCIP IV&quot;), whose general partner is Boylston Coinvestors, LLC (&quot;Boylston&quot;), sold 275,508 Common Shares. Following such sale, Glory IV held 1,589,676 Common Shares. BCIP IV may be deemed to beneficially own Common Shares held by Glory IV. BCIP IV disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F4">On August 18, 2017, Glory Investments IV-B Limited (&quot;Glory IV-B&quot; and together with Glory A, Glory B and Glory IV, the &quot;Glory Entities&quot;), whose Class A shareholder is BCIP Associates IV-B, L.P. (&quot;BCIP IV-B&quot;), whose general partner is Boylston, sold 20,744 shares of Common Stock. Following such sale, Glory IV-B held 119,702 Common Shares. BCIP IV-B may be deemed to beneficially own Common Shares held by Glory IV-B. BCIP IV-B disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F5">The governance, investment strategy and decision-making process with respect to investments held by the Glory Entities is directed by the Global Private Equity Board of BCI. By virtue of the relationships described in these footnotes, BCI may be deemed to share voting and dispositive power with respect to the Common Shares held by the Glory Entities. BCI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>BAIN CAPITAL INVESTORS, LLC, /s/ David Humphrey, Managing Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BAIN CAPITAL PARTNERS ASIA II, L.P., BY: BAIN CAPITAL INVESTORS, LLC, its general partner /s/ David Humphrey, Managing Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BAIN CAPITAL PARTNERS X, L.P., BY: BAIN CAPITAL INVESTORS, LLC, its general partner /s/ David Humphrey, Managing Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BCIP ASSOCIATES IV, L.P., BY: BOYLSTON COINVESTORS, LLC, its general partner /s/ David Humphrey, Authorized Signatory</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BCIP ASSOCIATES IV-B, L.P., BY: BOYLSTON COINVESTORS, LLC, its general partner /s/ David Humphrey, Authorized Signatory</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS A LIMITED, /s/ James Hildebrandt, Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS B LIMITED, /s/ James Hildebrandt, Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS IV LIMITED, /s/ James Hildebrandt, Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS IV-B LIMITED, /s/ James Hildebrandt, Director</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
