-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 QDJteNSyxMd2sLF57Zx68qvnuXpd9HD8m8194zJwpNmeJ2QyVkmR9K+fcA6+SIhf
 TUkBYfjJgmdjAIwSOEzNtw==

<SEC-DOCUMENT>0001005757-05-000005.txt : 20050105
<SEC-HEADER>0001005757-05-000005.hdr.sgml : 20050105
<ACCEPTANCE-DATETIME>20050105121510
ACCESSION NUMBER:		0001005757-05-000005
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050103
FILED AS OF DATE:		20050105
DATE AS OF CHANGE:		20050105

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CSG SYSTEMS INTERNATIONAL INC
		CENTRAL INDEX KEY:			0001005757
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROCESSING & DATA PREPARATION [7374]
		IRS NUMBER:				470783182
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		7887 EAST BELLEVIEW AVE
		STREET 2:		SUITE 1000
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80111
		BUSINESS PHONE:		3037962850

	MAIL ADDRESS:	
		STREET 1:		7887 E. BELLVIEW AVE.
		STREET 2:		SUITE 1000
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80111

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HANSEN NEAL C
		CENTRAL INDEX KEY:			0001031871

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27512
		FILM NUMBER:		05511159

	BUSINESS ADDRESS:	
		STREET 1:		C/O CSG SYSTEMS INTERNATIONAL INC (CSGS)
		STREET 2:		7887 E BELLEVIEW AVE SUITE 1000
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80111
		BUSINESS PHONE:		3037962860

	MAIL ADDRESS:	
		STREET 1:		C/O CSG SYSTEMS INTERNATIONAL INC(CSGS)
		STREET 2:		7887 E BELLEVIEW AVE SUITE 1000
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80111
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001031871d20050104f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-01-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001005757</issuerCik>
        <issuerName>CSG SYSTEMS INTERNATIONAL INC</issuerName>
        <issuerTradingSymbol>CSGS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001031871</rptOwnerCik>
            <rptOwnerName>HANSEN NEAL C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7887 E. BELLEVIEW AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1000</rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman &amp; CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-01-03</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2005-01-03</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>44608</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>18.7</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>472340</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6700</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Partnership</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>21.125</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2002-01-20</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-01-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>80000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>80000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>NEAL C HANSEN</signatureName>
        <signatureDate>2005-01-04</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----