<SEC-DOCUMENT>0001127602-25-010160.txt : 20250320
<SEC-HEADER>0001127602-25-010160.hdr.sgml : 20250320
<ACCEPTANCE-DATETIME>20250320164135
ACCESSION NUMBER:		0001127602-25-010160
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250318
FILED AS OF DATE:		20250320
DATE AS OF CHANGE:		20250320

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Sullivan Michele
		CENTRAL INDEX KEY:			0002009605
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13695
		FILM NUMBER:		25757075

	MAIL ADDRESS:	
		STREET 1:		2195 ROBERT J. CONLAN BLVD., NE
		STREET 2:		APT. 311
		CITY:			PALM BAY
		STATE:			FL
		ZIP:			32905

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COMMUNITY FINANCIAL SYSTEM, INC.
		CENTRAL INDEX KEY:			0000723188
		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
		ORGANIZATION NAME:           	02 Finance
		IRS NUMBER:				161213679
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		5790 WIDEWATERS PKWY
		CITY:			DEWITT
		STATE:			NY
		ZIP:			13214
		BUSINESS PHONE:		8007242262

	MAIL ADDRESS:	
		STREET 1:		5790 WIDEWATERS PARKWAY
		CITY:			DEWITT
		STATE:			NY
		ZIP:			13214

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	COMMUNITY BANK SYSTEM, INC.
		DATE OF NAME CHANGE:	20130806

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	COMMUNITY BANK NA, a subsidiary of Community Bank System Inc
		DATE OF NAME CHANGE:	20130729

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	COMMUNITY BANK NA, a subsidiary of Community Bank System Inc.
		DATE OF NAME CHANGE:	20130726
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-03-18</periodOfReport>

    <issuer>
        <issuerCik>0000723188</issuerCik>
        <issuerName>COMMUNITY FINANCIAL SYSTEM, INC.</issuerName>
        <issuerTradingSymbol>CBU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002009605</rptOwnerCik>
            <rptOwnerName>Sullivan Michele</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O COMMUNITY FINANCIAL SYSTEM, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>5790 WIDEWATERS PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>DEWITT</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>13214</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock (Deferred Stock Units)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-03-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1225</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1225</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2655.373</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Stock (Deferred Compensation)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-03-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>344.9465</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>57.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>344.9465</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1715.0923</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person has received deferred stock units under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the &quot;Plan&quot;). Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Financial System, Inc. common stock and will be settled in common stock at a predetermined date.</footnote>
        <footnote id="F2">Includes 13.032, 11.2154, and 11.1256 units of phantom stock acquired as dividend equivalents on July 10, 2024, October 10, 2024, and January 10, 2025, respectively, under the Plan.</footnote>
        <footnote id="F3">Each unit of phantom stock is the economic equivalent of one share of Community Financial System, Inc. common stock.  The units of phantom stock relating to the Deferred Compensation Plan will be settled in Community Financial System, Inc. common stock at future dates selected by the reporting person.</footnote>
        <footnote id="F4">Includes 8.1166 units of phantom stock acquired as dividend equivalents on January 10, 2025 under the Deferred Compensation Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Danielle M. Cima, pursuant to Confirming Statement executed by Michele Sullivan</signatureName>
        <signatureDate>2025-03-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
