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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001261031</rptOwnerCik>
            <rptOwnerName>MCNAMARA MICHAEL M</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>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2018-06-27</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>45269</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.3302</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3466532</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Disposition of shares exempt under Rule 16b-3 as payment of tax liability to Company incident to vesting of restricted stock share award.</footnote>
        <footnote id="F2">Price reflects weighted average sales price; actual sales prices ranged from $14.21 to $14.41. The Reporting Person undertakes to provide, upon request by the Commission staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares purchased or sold at each separate price.</footnote>
        <footnote id="F3">Includes the following: (1) 89,876 unvested Restricted Share Units, which will vest on June 10, 2019; (2) 183,308 unvested Restricted Share Units, which will vest in two equal annual installments beginning on June 14, 2019; (3) 336,597 unvested Restricted Share Units, which will vest in four equal annual installments beginning on June 29, 2018; and (4) 329,225 unvested Restricted Share Units, which will vest in four equal annual installments beginning on June 19, 2019.</footnote>
        <footnote id="F4">Each unvested Restricted Share Unit represents a contingent right to receive one unrestricted, fully transferable share for each vested Restricted Share Unit which has not previously forfeited.</footnote>
        <footnote id="F5">The shares are held by the McNamara Family Trust.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael McNamara, by David Bennett as attorney-in-fact</signatureName>
        <signatureDate>2018-06-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
