-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 drzWaMbRx7XMJaqwdGH3Jw==

<SEC-DOCUMENT>0001140361-09-015979.txt : 20090706
<SEC-HEADER>0001140361-09-015979.hdr.sgml : 20090703
<ACCEPTANCE-DATETIME>20090706185608
ACCESSION NUMBER:		0001140361-09-015979
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090701
FILED AS OF DATE:		20090706
DATE AS OF CHANGE:		20090706

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UIL HOLDINGS CORP
		CENTRAL INDEX KEY:			0001082510
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC SERVICES [4911]
		IRS NUMBER:				061541045
		STATE OF INCORPORATION:			CT
		FISCAL YEAR END:			0427

	BUSINESS ADDRESS:	
		STREET 1:		157 CHURCH ST
		CITY:			NEW HAVEN
		STATE:			CT
		ZIP:			06510
		BUSINESS PHONE:		2034992000

	MAIL ADDRESS:	
		STREET 1:		157 CHURCH ST
		CITY:			NEW HAVEN
		STATE:			CT
		ZIP:			06510

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Murdy William F
		CENTRAL INDEX KEY:			0001205063

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-15052
		FILM NUMBER:		09932108

	MAIL ADDRESS:	
		STREET 1:		777 POST OAK BLVD., SUITE 500
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056

	FORMER NAME:	
		FORMER CONFORMED NAME:	MURDY WILLIAM F
		DATE OF NAME CHANGE:	20021109
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-07-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001082510</issuerCik>
        <issuerName>UIL HOLDINGS CORP</issuerName>
        <issuerTradingSymbol>UIL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001205063</rptOwnerCik>
            <rptOwnerName>Murdy William F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>157 CHURCH STREET</rptOwnerStreet1>
            <rptOwnerStreet2>P, O. BOX 1564</rptOwnerStreet2>
            <rptOwnerCity>NEW HAVEN</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06510</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>22.96</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-07-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>378.999</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>22.96</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2012-03-23</value>
            </exerciseDate>
            <expirationDate>
                <value>2012-03-23</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>378.999</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20522.104</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>22.96</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-07-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>333.032</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>22.96</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>1988-08-08</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>1988-08-08</value>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>333.032</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18033.086</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">As a result of a timely deferral election, payment of a cash fee for service as a non-employee director has been deferred and is deemed to be invested in phantom stock units pursuant to the terms of the UIL Holdings Corporation Non-Employee Directors Common Stock and Deferred Compensation Plan.  Phantom Stock Units are credited quarterly with dividend equivalents and are paid in the form of the Issuer's Common Stock upon distribution.</footnote>
        <footnote id="F2">Grant of restricted stock for service as a non-employee director.  As a result of a timely deferreal election, the award of restricted stock was automatically converted to an award of restricted stock units that are deferred pursuant to the terms of the UIL Holdings Corporation Deferred Compensation Plan.  Deferred restricted stock units are credited quarterly with dividend equivalents, and are paid in the form of the Issuer's Common Stock upon distribution.</footnote>
        <footnote id="F3">The Staff has designated &quot;08/08/1988&quot; as a dummy date for this specific purpose.</footnote>
        <footnote id="F4">The Staff has designated &quot;08/08/1988&quot; as a dummy date for this specific purpose.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Susan E. Allen, attorney-in-fact</signatureName>
        <signatureDate>2009-07-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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