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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-01-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001464790</issuerCik>
        <issuerName>B. Riley Financial, Inc.</issuerName>
        <issuerTradingSymbol>RILY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001251859</rptOwnerCik>
            <rptOwnerName>ASHER DANIEL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>111 W JACKSON BLVD</rptOwnerStreet1>
            <rptOwnerStreet2>20TH FL</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60604</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock with a par value of $0.0001</value>
            </securityTitle>
            <transactionDate>
                <value>2017-01-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.8</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2353738</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock with a par value of $0.0001</value>
            </securityTitle>
            <transactionDate>
                <value>2017-01-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>15</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2353723</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">2,000,000 of the securities are held of record by DJ Fund Investments, LLC - Series E (&quot;DJ Fund&quot;). Fred Goldman (&quot;Goldman&quot;) and Michael LaRocque (&quot;LaRocque&quot;), both natural persons, are managers of DJ Fund. The Reporting Person, a natural person, is a member and holder of less than 50% of the membership interests of DJ Fund. DJ Fund, Goldman, LaRocque and the Reporting Person have entered into an informal unwritten agreement that provides the Reporting Person with investment and voting power over the securities. By virtue of these relationships, Goldman, LaRocque and the Reporting Person may be deemed to have voting and investment power over the securities held by DJ Fund and as a result may be deemed to have beneficial ownership over such securities. Both Goldman and LaRocque disclaim beneficial ownership of the securities.</footnote>
        <footnote id="F2">The securities were sold  through, and are held of record in, a brokerage account of Equitec Proprietary Market, LLC attributed to the Reporting Person's name.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Daniel Asher</signatureName>
        <signatureDate>2017-01-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
