<SEC-DOCUMENT>0001213900-21-020238.txt : 20210405
<SEC-HEADER>0001213900-21-020238.hdr.sgml : 20210405
<ACCEPTANCE-DATETIME>20210405202158
ACCESSION NUMBER:		0001213900-21-020238
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210401
FILED AS OF DATE:		20210405
DATE AS OF CHANGE:		20210405

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ECP ControlCo, LLC
		CENTRAL INDEX KEY:			0001707921
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38186
		FILM NUMBER:		21807720

	BUSINESS ADDRESS:	
		STREET 1:		40 BEECHWOOD ROAD
		CITY:			SUMMIT
		STATE:			NJ
		ZIP:			07901
		BUSINESS PHONE:		(973) 671-6100

	MAIL ADDRESS:	
		STREET 1:		40 BEECHWOOD ROAD
		CITY:			SUMMIT
		STATE:			NJ
		ZIP:			07901

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Energy Capital Partners Management, LP
		CENTRAL INDEX KEY:			0001815150
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38186
		FILM NUMBER:		21807718

	BUSINESS ADDRESS:	
		STREET 1:		51 JOHN F. KENNEDY PARKWAY
		STREET 2:		SUITE 200
		CITY:			SHORT HILLS
		STATE:			NJ
		ZIP:			07078
		BUSINESS PHONE:		(973) 671-6100

	MAIL ADDRESS:	
		STREET 1:		51 JOHN F. KENNEDY PARKWAY
		STREET 2:		SUITE 200
		CITY:			SHORT HILLS
		STATE:			NJ
		ZIP:			07078

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ECP Management GP, LLC
		CENTRAL INDEX KEY:			0001815147
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38186
		FILM NUMBER:		21807719

	BUSINESS ADDRESS:	
		STREET 1:		51 JOHN F. KENNEDY PARKWAY
		STREET 2:		SUITE 200
		CITY:			SHORT HILLS
		STATE:			NJ
		ZIP:			07078
		BUSINESS PHONE:		(973) 671-6100

	MAIL ADDRESS:	
		STREET 1:		51 JOHN F. KENNEDY PARKWAY
		STREET 2:		SUITE 200
		CITY:			SHORT HILLS
		STATE:			NJ
		ZIP:			07078

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Custom Truck One Source, Inc.
		CENTRAL INDEX KEY:			0001709682
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-EQUIPMENT RENTAL & LEASING, NEC [7359]
		IRS NUMBER:				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>
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<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-04-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001707921</rptOwnerCik>
            <rptOwnerName>ECP ControlCo, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>40 BEECHWOOD ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUMMIT</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001815147</rptOwnerCik>
            <rptOwnerName>ECP Management GP, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>40 BEECHWOOD ROAD,</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUMMIT</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001815150</rptOwnerCik>
            <rptOwnerName>Energy Capital Partners Management, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>40 BEECHWOOD ROAD,</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUMMIT</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-04-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>60000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25738988</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-04-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>13631</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F6"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13631</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13631</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-04-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>60000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F7"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>60000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents securities held directly by Energy Capital Partners Management, LP (&quot;ECP Management&quot;). Each of Jennifer Gray, Rahman D'Argenio, Matthew Himler and Douglas Kimmelman have entered into an agreement with ECP Mangement pursuant to which he or she has irrevocably assigned any and all compensation, including the equity award reported herein, that he or she may receive from serving as a director of the Issuer to ECP Management. ECP Management GP, LLC is the general partner of ECP Management and may be deemed to share beneficial ownership of the securities held by ECP Management.</footnote>
        <footnote id="F2">Represents securities held directly by the following entities in the following amounts: NESCO Holdings, LP - 21,238,988, Energy Capital Partners III, LP (&quot;ECP III&quot;) - 64,450, Energy Capital Partners III-A, LP (&quot;III-A&quot;) - 2,169,601, Energy Capital Partners III-B, LP (&quot;III-B&quot;) - 262,015, Energy Capital Partners III-C, LP (&quot;III-C&quot;) - 896,947, Energy Capital Partners III-D, LP (&quot;III-D&quot;) - 1,106,987.</footnote>
        <footnote id="F3">The general partner of NESCO Holdings, LP is NESCO Holdings GP, LLC. The members of NESCO Holdings GP, LLC are ECP III, III-A, III-B, III-C, III-D, and Energy Capital Partners III (NESCO Co-Invest), LP (&quot;NESCO Co-Invest&quot;). The general partner of ECP III, III-A, III-B, III-C, and III-D is Energy Capital Partners GP III, LP (&quot;ECP III GP LP&quot;), and the general partner of ECP III GP LP is Energy Capital Partners III, LLC (&quot;ECP III GP LLC&quot;). The general partner of NESCO Co-Invest is Energy Capital Partners GP III Co-Investment (NESCO), LLC, and the managing member of Energy Capital Partners GP III Co-Investment (NESCO), LLC is ECP III GP LLC. As a result, each of the foregoing entities may be deemed to share beneficial ownership of the securities held by Nesco Holdings, LP.</footnote>
        <footnote id="F4">ECP ControlCo, LLC (&quot;ECP ControlCo&quot;) is the managing member of ECP III GP LLC and the sole member of ECP Management GP, LLC. As a result, ECP ControlCo may be deemed to share beneficial ownership of the securities beneficially owned by ECP III GP LLC and ECP Management GP, LLC. The managing members of ECP ControlCo are Douglas Kimmelman, Andrew Singer, Peter Labbat, Tyler Reeder and Rahman D'Argenio all of whom collectively share the power to vote and dispose of the securities beneficially owned by ECP ControlCo. Each such individual disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F5">Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock.</footnote>
        <footnote id="F6">The restricted stock units will vest on March 31, 2022 and have no expiration date.</footnote>
        <footnote id="F7">In connection with the acquisition of Custom Truck One Source, L.P. by the Issuer, these restricted stock units automatically vested.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>ECP ControlCo, LLC By: /s/ Rahman D'Argenio, Managing Member</signatureName>
        <signatureDate>2021-04-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ECP Management GP, LLC By: ECP ControlCo, LLC, its sole member By: /s/ Rahman D'Argenio, Managing Member</signatureName>
        <signatureDate>2021-04-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ECP ControlCo, LLC By: ECP Management GP, LLC, its general partner By: ECP ControlCo, LLC, its sole member By: /s/ Rahman D'Argenio, Managing Member</signatureName>
        <signatureDate>2021-04-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
