<SEC-DOCUMENT>0001213900-25-037888.txt : 20250430
<SEC-HEADER>0001213900-25-037888.hdr.sgml : 20250430
<ACCEPTANCE-DATETIME>20250430191110
ACCESSION NUMBER:		0001213900-25-037888
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250428
FILED AS OF DATE:		20250430
DATE AS OF CHANGE:		20250430

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BARRETT RAYMOND TODD
		CENTRAL INDEX KEY:			0001785100
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38186
		FILM NUMBER:		25898522

	MAIL ADDRESS:	
		STREET 1:		6714 POINT INVERNESS WAY
		STREET 2:		STE 220
		CITY:			FORT WAYNE
		STATE:			IN
		ZIP:			46804

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Custom Truck One Source, Inc.
		CENTRAL INDEX KEY:			0001709682
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-EQUIPMENT RENTAL & LEASING, NEC [7359]
		ORGANIZATION NAME:           	07 Trade & Services
		EIN:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		7701 INDEPENDENCE AVENUE
		CITY:			KANSAS CITY
		STATE:			MO
		ZIP:			64125
		BUSINESS PHONE:		(816) 241-4888

	MAIL ADDRESS:	
		STREET 1:		7701 INDEPENDENCE AVENUE
		CITY:			KANSAS CITY
		STATE:			MO
		ZIP:			64125

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NESCO HOLDINGS, INC.
		DATE OF NAME CHANGE:	20190730

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Capitol Investment Corp. IV
		DATE OF NAME CHANGE:	20170619
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>ownership.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-04-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001709682</issuerCik>
        <issuerName>Custom Truck One Source, Inc.</issuerName>
        <issuerTradingSymbol>CTOS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001785100</rptOwnerCik>
            <rptOwnerName>BARRETT RAYMOND TODD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7701 INDEPENDENCE AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KANSAS CITY</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64125</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Accounting Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-04-28</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock.</footnote>
        <footnote id="F2">The restricted stock units vest in four equal annual installments beginning on April 1, 2026, subject to continued service on the applicable vesting date and potential partial acceleration upon the achievement of certain corporate milestones.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Paul M. Jolas, Attorney-in-fact</signatureName>
        <signatureDate>2025-04-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
