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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-12-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000866374</issuerCik>
        <issuerName>FLEX LTD.</issuerName>
        <issuerTradingSymbol>FLEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001504430</rptOwnerCik>
            <rptOwnerName>OFFER DAVID SCOTT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FLEXTRONICS INTERNATIONAL USA, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>6201 AMERICA CENTER DRIVE</rptOwnerStreet2>
            <rptOwnerCity>SAN JOSE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP, General Counsel</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2018-12-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>59453</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>370618</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Consists of 59,453 Restricted Share Units (&quot;RSUs&quot;) which will vest subject to the Reporting Person's continued employment through the applicable measurement date and upon achievement of performance conditions as follows: (i) 50% of the RSUs will vest if the closing trading price of the ordinary shares exceeds $12.00 (the &quot;Hurdle Price&quot;) for any 20 consecutive trading days during the period between the first and second anniversaries of the date of grant, and (ii) 50% of the RSUs will vest if the closing trading price of the ordinary shares exceeds the Hurdle Price for any 20 consecutive trading days during the period between the second and third anniversaries of the date of grant; provided that if the RSUs do not vest under (i), 100% of the RSUs will vest if the conditions in (ii) are satisfied.</footnote>
        <footnote id="F2">Includes the following: (1) 90,000 unvested RSUs, which will vest in two equal installments beginning on November 30, 2019; (2) 50,000 unvested RSUs, which will vest on November 30, 2019;  (3) 40,162 unvested RSUs, which will vest in three equal installments beginning on June 29, 2019; (4) 52,376 unvested RSUs, which will vest in four equal installments beginning on June 19, 2019; and (5) 59,453 unvested RSUs, which will vest as provided in footnote 1 above.</footnote>
        <footnote id="F3">Each unvested RSU represents a contingent right to receive one unrestricted, fully transferable share for each vested RSU which has not previously forfeited.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David Scott Offer, by Heather Childress as attorney-in-fact</signatureName>
        <signatureDate>2018-12-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
