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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-06-11</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>2019-06-11</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>91146</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>704482</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Consists of 91,146 unvested restricted share units (&quot;RSUs&quot;), which will vest in four equal annual installments beginning on June 11, 2020.</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; (5) 91,146 unvested RSUs, which will vest in four equal installments beginning on June 11, 2020; (6) 59,453 unvested RSUs, which will vest upon achievement of performance conditions; and (7) 242,718 unvested RSUs, which will vest on March 5, 2021.</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>2019-06-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
