-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 BRrbd9j6N3m68DLNdOT87pl6w3QPCjdqLIjB9+/bou/UVBPBwHHHY5EFOhCtnjR1
 Jc314ZaylPiQbMeBp4mt1A==

<SEC-DOCUMENT>0001237699-09-000005.txt : 20090916
<SEC-HEADER>0001237699-09-000005.hdr.sgml : 20090916
<ACCEPTANCE-DATETIME>20090916141820
ACCESSION NUMBER:		0001237699-09-000005
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090914
FILED AS OF DATE:		20090916
DATE AS OF CHANGE:		20090916

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			TILLETT RONALD L
		CENTRAL INDEX KEY:			0001237699

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20293
		FILM NUMBER:		091071785

	MAIL ADDRESS:	
		STREET 1:		PO BOX 446
		CITY:			BOWLING GREEN
		STATE:			VA
		ZIP:			22427

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNION BANKSHARES CORP
		CENTRAL INDEX KEY:			0000883948
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				540412820
		STATE OF INCORPORATION:			VA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		211 NORTH MAIN ST
		STREET 2:		P O BOX 446
		CITY:			BOWLING GREEN
		STATE:			VA
		ZIP:			22427
		BUSINESS PHONE:		8046335031

	MAIL ADDRESS:	
		STREET 1:		PO BOX 446
		STREET 2:		211 NORTH MAIN ST
		CITY:			BOWLING GREEN
		STATE:			VA
		ZIP:			22427

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	UNION BANCORP INC /VA/
		DATE OF NAME CHANGE:	19930328
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-09-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000883948</issuerCik>
        <issuerName>UNION BANKSHARES CORP</issuerName>
        <issuerTradingSymbol>ubsh</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237699</rptOwnerCik>
            <rptOwnerName>TILLETT RONALD L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PO BOX 446</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOWLING GREEN</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22427</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>2009-09-14</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>13.26</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13936</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>/s/ Ronald L. Tillett</signatureName>
        <signatureDate>2009-09-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----