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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-08-20</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001164552</issuerCik>
        <issuerName>CDSS Wind Down Inc</issuerName>
        <issuerTradingSymbol>CWDW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001213709</rptOwnerCik>
            <rptOwnerName>WEINSTEIN ROBERT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GREEN ENERGY MANAGEMENT SERVICES INC</rptOwnerStreet1>
            <rptOwnerStreet2>381 TEANECK ROAD</rptOwnerStreet2>
            <rptOwnerCity>TEANECK</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07666</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.0001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2010-08-20</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5495184</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5495184</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">In accordance with the Merger Agreement, dated as of March 29, 2010, as amended, by and among Green Energy Management Services, Inc. (&quot;GEM&quot;), the Issuer, and the Issuer's wholly-owned merger subsidiary (the &quot;Merger Subsidiary&quot;), CDSS Merger Corporation, pursuant to which on August 20, 2010, the Merger Subsidiary merged with and into GEM, with GEM being the surviving corporation, and became a wholly-owned subsidiary of the Issuer, all of the Reporting Person's shares of GEM common stock were converted into 5,495,184 post-reverse stock split shares of the Issuer's common stock.</footnote>
        <footnote id="F2">Reported shares will vest monthly at a rate of 1/24 beginning on the 15th day of each month following April 15, 2010, if the Reporting Person continues to be employed by the Issuer or GEM on each monthly vesting date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Robert Weinstein</signatureName>
        <signatureDate>2010-08-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
