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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-09-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001414932</issuerCik>
        <issuerName>Fifth Street Finance Corp.</issuerName>
        <issuerTradingSymbol>FSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001200461</rptOwnerCik>
            <rptOwnerName>TANNENBAUM LEONARD M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FIFTH STREET (FSC),</rptOwnerStreet1>
            <rptOwnerStreet2>777 WEST PUTNAM AVENUE, 3RD FLOOR</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001611988</rptOwnerCik>
            <rptOwnerName>Fifth Street Asset Management Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>777 WEST PUTNAM AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>3RD FLOOR</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001643561</rptOwnerCik>
            <rptOwnerName>Fifth Street Holdings L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>777 WEST PUTNAM AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>3RD FLOOR</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>PSA in respect of Swaps</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.25</value>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-09-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>X</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-09-07</value>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3878542</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Partnership</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each of Mr. Tannenbaum, Fifth Street Asset Management Inc. and Fifth Street Holdings L.P. (&quot;FSH&quot;) (together, the &quot;Reporting Persons&quot;) is a party to the Purchase and Settlement Agreement, dated as of February 18, 2016 ( the &quot;PSA&quot;), entered into by and among Fifth Street Finance Corp. (the &quot;Company&quot;), the Reporting Persons and the Sellers (as defined below). The &quot;Sellers&quot; are RiverNorth Capital Management, LLC, RiverNorth Capital Partners, L.P., RiverNorth Institutional Partners, L.P., RiverNorth Core Opportunity Fund, RiverNorth/DoubleLine Strategic Income Fund (collectively, the &quot;RiverNorth Parties&quot;), Randy I. Rochman, Fred G. Steingraber and Murray R. Wise. Pursuant to the PSA, the Reporting Persons agreed with the counterparties (the &quot;Counterparties&quot; and each a &quot;Counterparty&quot;) to certain cash-settled total return swap agreements (the &quot;Swaps&quot; and each a &quot;Swap&quot;) in reference to an aggregate 3,878,542 shares of Company common stock, par value $0.01 per share (continued in footnote 2)</footnote>
        <footnote id="F2">(the &quot;Common Stock&quot;) that upon the applicable valuation or deemed valuation of any such Swap, (i) if in any case the final price applicable to such Swap, as between the applicable Counterparty and the bank with which the applicable Counterparty had entered into such Swap (or deemed final price deemed applicable under the PSA), was greater than $6.25 per share, then such Counterparty shall pay to FSH a sum in cash equal to the number of shares referenced by such Swap multiplied by the excess of such final price over $6.25, and (ii) if in any case such final price (or deemed final price applicable under the PSA) was less than $6.25 per share, then FSH shall pay to such Counterparty a sum in cash equal to the number of shares referenced by such Swap multiplied by the excess of $6.25 over such final price. On September 7, 2016, FSH and the Counterparties agreed that the amount then due from FSH to the Counterparties under the terms of the PSA was $160,265.90. (continued in footnote 3)</footnote>
        <footnote id="F3">On that date, the Reporting Persons and the RiverNorth Parties entered into the Mutual Release and Waiver of Rights under the PSA (the &quot;Mutual Release and Waiver&quot;) pursuant to which the Reporting Persons paid the Counterparties or their affiliates the entire amount of $160,265.90 then due under the PSA (such payment, the &quot;Swap Settlement&quot;).  As a result of the Swap Settlement, the Reporting Persons no longer have a pecuniary interest in the Swaps.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Leonard M. Tannenbaum</signatureName>
        <signatureDate>2016-09-09</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>FIFTH STREET ASSET MANAGEMENT INC., By: /s/ Leonard M. Tannenbaum</signatureName>
        <signatureDate>2016-09-09</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>FIFTH STREET HOLDINGS, L.P., By: Fifth Street Asset Management Inc., its General Partner, By: /s/ Leonard M. Tannenbaum</signatureName>
        <signatureDate>2016-09-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
