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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001528985</issuerCik>
        <issuerName>Inland Real Estate Income Trust, Inc.</issuerName>
        <issuerTradingSymbol>n/a</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001444690</rptOwnerCik>
            <rptOwnerName>Daniels Lee A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2901 BUTTERFIELD ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OAK BROOK</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60523</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Share Units</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-06-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>559.284</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>559.284</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1077.894</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Restricted share units (RSUs) were granted to the reporting person pursuant to the Issuer's Employee and Director Restricted Share Plan.  Each RSU represents the right to receive one share of the Issuer's common stock and an amount equal to the cash value of the dividends that would have been paid to the reporting person if one share of common stock had been issued on the grant date for each RSU granted to the reporting person under this award.  These RSUs were issued on account of the reporting person's service as a non-employee director of the Issuer and without additional consideration.  The RSUs become vested in equal installments of 33-1/3% on 6/12/19, 6/12/20 and 6/12/21, subject to the reporting person's continued service to the Issuer; provided that 100% of any then unvested RSUs becomes fully vested upon the consummation of a liquidity event or termination of the reporting person's service to the Issuer by reason of death or disability.</footnote>
        <footnote id="F2">The RSUs will be settled in shares of common stock on the earliest of:  6/1/20, upon the reporting person's death, upon the reporting person's disability, upon the reporting person's separation from service or upon a change in control event.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Roberta S. Matlin, Vice President</signatureName>
        <signatureDate>2018-06-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
