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

    <schemaVersion>X0304</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-09-06</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>1411 E MISSION AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SPOKANE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>99220</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>2011-09-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>249</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>24.03</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12674</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>9600</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 director compensation utilizing &quot;new issue&quot; stock price.  The price per share (per LTIP) is the closing price on Friday, September 2, 2011.</footnote>
        <footnote id="F2">Shares issued as part of Ms. Stanley's director retainer.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Heidi B Stanley</signatureName>
        <signatureDate>2011-09-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0304
4
2011-09-06
0
0000104918
AVISTA CORP
AVA
0001253138
STANLEY HEIDI B
1411 E MISSION AVE
SPOKANE
WA
99220
1
0
0
0
Common Stock
2011-09-06
4
A
0
249
24.03
A
12674
D
Common Stock held in Spouse's Profit Sharing Plan
9600
I
by Trustee
Shares issued under the Long Term Incentive Plan (LTIP) as an award of stock for director compensation utilizing "new issue" stock price.  The price per share (per LTIP) is the closing price on Friday, September 2, 2011.
Shares issued as part of Ms. Stanley's director retainer.
/s/ Heidi B Stanley
2011-09-07