<SEC-DOCUMENT>0001628280-18-003959.txt : 20180403
<SEC-HEADER>0001628280-18-003959.hdr.sgml : 20180403
<ACCEPTANCE-DATETIME>20180403165105
ACCESSION NUMBER:		0001628280-18-003959
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180402
FILED AS OF DATE:		20180403
DATE AS OF CHANGE:		20180403

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Celaya Jorge
		CENTRAL INDEX KEY:			0001406206

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51813
		FILM NUMBER:		18734138

	MAIL ADDRESS:	
		STREET 1:		1920 L STREET NW
		STREET 2:		6TH FLOOR
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20036

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LIQUIDITY SERVICES INC
		CENTRAL INDEX KEY:			0001235468
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-BUSINESS SERVICES, NEC [7389]
		IRS NUMBER:				522209244
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		6931 ARLINGTON ROAD
		STREET 2:		SUITE 200
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
		BUSINESS PHONE:		2024676868

	MAIL ADDRESS:	
		STREET 1:		6931 ARLINGTON ROAD
		STREET 2:		SUITE 200
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_152278862521329.xml
<DESCRIPTION>FORM 4
<TEXT>
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    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-04-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001235468</issuerCik>
        <issuerName>LIQUIDITY SERVICES INC</issuerName>
        <issuerTradingSymbol>LQDT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001406206</rptOwnerCik>
            <rptOwnerName>Celaya Jorge</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LIQUIDITY SERVICES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>6931 ARLINGTON ROAD, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>BETHESDA</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20814</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
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            <transactionAmounts>
                <transactionShares>
                    <value>2425</value>
                </transactionShares>
                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
                    <value>A</value>
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                <footnoteId id="F5"/>
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            <expirationDate>
                <value>2025-10-01</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                <underlyingSecurityShares>
                    <value>6335.0</value>
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            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6335</value>
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                    <value>D</value>
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            <expirationDate>
                <value>2025-10-01</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13891.0</value>
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            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13891</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        <derivativeHolding>
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            <expirationDate>
                <value>2025-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3473.0</value>
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            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3473</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
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        <derivativeHolding>
            <securityTitle>
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            <conversionOrExercisePrice>
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                <sharesOwnedFollowingTransaction>
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            <transactionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
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            <transactionAmounts>
                <transactionShares>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                <underlyingSecurityShares>
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                    <value>3120</value>
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                <directOrIndirectOwnership>
                    <value>D</value>
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            <securityTitle>
                <value>Employee Stock Option</value>
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                <value>4.47</value>
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                <footnoteId id="F10"/>
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            <expirationDate>
                <value>2027-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20280.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20280</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Grant</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.47</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F11"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2080.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>2080</value>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
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    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the vesting of restricted stock.</footnote>
        <footnote id="F2">Represents an advance election by the insider to satisfy tax withholding obligations related to vesting of restricted shares by authorizing the issuer to sell a number of shares with an aggregate fair market value that would satisfy the withholding amount due.</footnote>
        <footnote id="F3">Twenty-five percent of this restricted stock grant vested on October 1, 2016 and thereafter 1/4 of the restricted stock grant will vest on October 1 of each year for three years. In the event that Mr. Celaya's employment is terminated by the Company without cause or by Mr. Celaya for good reason within his first eighteen months of employment, 37.5 percent of this restricted stock grant will become vested as of the date of his termination. On the eighteen month anniversary of Mr. Celaya's start of employment, this acceleration provision will expire.</footnote>
        <footnote id="F4">Twenty-five percent of this restricted stock grant vested on October 1, 2016 and thereafter 1/4th of the restricted stock grant will vest on October 1 of each year for three years.</footnote>
        <footnote id="F5">These restricted shares will vest, if at all, based on the Issuer's achievement of certain financial milestones.</footnote>
        <footnote id="F6">Twenty-five percent of this option grant vested on October 1, 2016 and thereafter 1/48th of the option grant will vest each month for thirty-six months.</footnote>
        <footnote id="F7">This option becomes exercisable, if at all, based on the Issuer's achievement of certain financial milestones.</footnote>
        <footnote id="F8">Twenty-five percent of this restricted stock grant vested on April 1, 2018 and thereafter 1/4th of the restricted stock grant will vest on each of October 1, 2018, October 1, 2019, and October 1, 2020.</footnote>
        <footnote id="F9">18/48th of this option grant vested on April 1, 2018 and thereafter 1/48th of the option grant will vest each month for thirty months.</footnote>
        <footnote id="F10">15/48th of this option grant will vest on January 1, 2019 and thereafter 1/48th of the option grant will vest each month for thirty three months.</footnote>
        <footnote id="F11">Twenty-five percent of this restricted stock grant will vest on January 1, 2019 and thereafter 1/4th of the restricted stock grant will vest on each October 1, 2019, October 1, 2020, and October 1, 2021.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark A. Shaffer, by power of attorney</signatureName>
        <signatureDate>2018-04-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
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</SEC-DOCUMENT>
