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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-08-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000776901</issuerCik>
        <issuerName>INDEPENDENT BANK CORP</issuerName>
        <issuerTradingSymbol>INDB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001207141</rptOwnerCik>
            <rptOwnerName>GILMORE BENJAMIN A II</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O INDEPENDENT BANK CORP</rptOwnerStreet1>
            <rptOwnerStreet2>288 UNION STREET</rptOwnerStreet2>
            <rptOwnerCity>ROCKLAND</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02370</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>2009-08-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>46.8546</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.3426</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13242.8482</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares, which were purchased through an optional cash purchase feature of the Company's Dividend Reinvestment Plan, were inadvertently included in shares purchased with reinvested dividends which were reported in the total holdings of the Form 4 filed on May 26, 2010.</footnote>
        <footnote id="F2">Total holdings include 107.103555 shares received between 5/09 and 8/09 as a result of participation in the Independent Bank Corp. Dividend Reinvestment Plan.  Such transactions are exempt from the reporting requirements of Section 16 of the Securities and Exchange Act of 1934, as amended.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Linda M. Campion, Power of Attorney for Benjamin A. Gilmore, II</signatureName>
        <signatureDate>2010-06-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
