<?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>0001330988</rptOwnerCik>
            <rptOwnerName>Britt Douglas</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6201 AMERICA CENTER DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></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>President</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>303458</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5444</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </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) 20,661 unvested RSUs, which will vest on June 10, 2019; (2) 39,002 unvested RSUs, which will vest in two equal annual installments beginning on June 14, 2019; (3) 50,490 unvested RSUs, which will vest in three equal annual installments beginning on June 29, 2019; (4) 76,899 unvested RSUs, which will vest in four equal annual 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>
        <footnote id="F4">Includes 2,855 unvested RSUs, which will vest in four equal annual installments beginning on June 14, 2019.</footnote>
        <footnote id="F5">The Reporting Person disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

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