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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-09-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000104918</issuerCik>
        <issuerName>AVISTA CORP</issuerName>
        <issuerTradingSymbol>AVA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001253138</rptOwnerCik>
            <rptOwnerName>STANLEY HEIDI B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>111 NORTH WALL STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SPOKANE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>99201-0696</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-09-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>312</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.35</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12225</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock Held in Spouse's Profit Sharing Plan</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9660</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trustee</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares issued under the Long Term Incentive Plan (LTIP) as an award of stock for directors compensation.  The price per share (per the LTIP) is the closing price on September 1, 2010</footnote>
        <footnote id="F2">Shares issued as part of Ms. Stanley's director retainer.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Heidi B Stanley</signatureName>
        <signatureDate>2010-09-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2010-09-02
0
0000104918
AVISTA CORP
AVA
0001253138
STANLEY HEIDI B
111 NORTH WALL STREET
SPOKANE
WA
99201-0696
1
0
0
0
Common Stock
2010-09-02
4
A
0
312
21.35
A
12225
D
Common Stock Held in Spouse's Profit Sharing Plan
9660
I
By Trustee
Shares issued under the Long Term Incentive Plan (LTIP) as an award of stock for directors compensation.  The price per share (per the LTIP) is the closing price on September 1, 2010
Shares issued as part of Ms. Stanley's director retainer.
/s/ Heidi B Stanley
2010-09-02