<SEC-DOCUMENT>0001628280-18-001043.txt : 20180205
<SEC-HEADER>0001628280-18-001043.hdr.sgml : 20180205
<ACCEPTANCE-DATETIME>20180205175351
ACCESSION NUMBER:		0001628280-18-001043
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180201
FILED AS OF DATE:		20180205
DATE AS OF CHANGE:		20180205

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GROSS PATRICK W
		CENTRAL INDEX KEY:			0001184343

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51813
		FILM NUMBER:		18575493

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_151787121634098.xml
<DESCRIPTION>FORM 4
<TEXT>
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    <periodOfReport>2018-02-01</periodOfReport>

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

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            <rptOwnerName>GROSS PATRICK W</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>
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        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
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        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option</value>
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            <conversionOrExercisePrice>
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            <exerciseDate>
                <footnoteId id="F6"/>
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            <expirationDate>
                <value>2019-04-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>21086.0</value>
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            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21086</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option</value>
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            <conversionOrExercisePrice>
                <value>10.7</value>
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            <exerciseDate>
                <footnoteId id="F7"/>
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            <expirationDate>
                <value>2020-02-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18612.0</value>
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            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18612</value>
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                <sharesOwnedFollowingTransaction>
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        <derivativeHolding>
            <securityTitle>
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            <conversionOrExercisePrice>
                <value>21.53</value>
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            <expirationDate>
                <value>2024-02-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                <underlyingSecurityShares>
                    <value>20061.0</value>
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                <sharesOwnedFollowingTransaction>
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                <transactionCode>J</transactionCode>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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                    <value>15128.0</value>
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                <directOrIndirectOwnership>
                    <value>D</value>
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            <securityTitle>
                <value>Employee Stock Grant</value>
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                <value>6.5</value>
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                <value>2018-02-01</value>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
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                <transactionShares>
                    <value>22692</value>
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                <transactionPricePerShare>
                    <value>0</value>
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                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F15"/>
            </exerciseDate>
            <expirationDate>
                <value>2028-02-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>22692.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>22692</value>
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                    <value>D</value>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the vesting of restricted stock.</footnote>
        <footnote id="F2">These options expired on April 3, 2016 without being exercised.</footnote>
        <footnote id="F3">These options expired on October 2, 2016 without being exercised.</footnote>
        <footnote id="F4">These options expired on October 1, 2017 without being exercised.</footnote>
        <footnote id="F5">These options became fully vested on June 3, 2009.</footnote>
        <footnote id="F6">These options became fully vested on February 18, 2010.</footnote>
        <footnote id="F7">These options became fully vested on February 1, 2011.</footnote>
        <footnote id="F8">These options became fully vested on February 1, 2012.</footnote>
        <footnote id="F9">These options became fully vested on February 1, 2013.</footnote>
        <footnote id="F10">These options became fully vested on February 1, 2014.</footnote>
        <footnote id="F11">These options became fully vested on February 1, 2015.</footnote>
        <footnote id="F12">These options became fully vested on February 1, 2016.</footnote>
        <footnote id="F13">These options became fully vested on February 1, 2017.</footnote>
        <footnote id="F14">These restricted shares became fully vested on February 1, 2018.</footnote>
        <footnote id="F15">These restricted shares have a one-year vesting period such that 100% of this restricted share grant will vest on February 1, 2019.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark A. Shaffer, by power of attorney</signatureName>
        <signatureDate>2018-02-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
