CTOS 13D/A: Mark Ein 5,159,319 shares, 2.3% stake

Custom Truck One Source (CTOS) filers submitted Amendment No. 1 to Schedule 13D to report an in-kind distribution and updated ownership.

Rhea-AI Filing Summary

Custom Truck One Source (CTOS) filers submitted Amendment No. 1 to Schedule 13D to report an in-kind distribution and updated ownership. On October 17, 2025, Capitol Acquisition Management IV LLC distributed 3,670,279 shares of common stock to its members on a pro rata basis; as part of this, Mark Ein acquired 3,553,612 shares.

Following the distribution, Mr. Ein reports beneficial ownership of 5,159,319 shares (including options to purchase 20,000 shares that are currently exercisable), representing 2.3% of the class. This percentage is based on 226,559,586 shares outstanding as of July 28, 2025, as disclosed in the issuer’s Form 10‑Q filed July 30, 2025. The filing states the reporting persons have ceased to be beneficial owners of more than five percent of the outstanding common stock. Other reporting persons listed report zero shares following the distribution.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did CTOS’s Schedule 13D/A disclose?

It reported an in-kind distribution of 3,670,279 shares to members of Capitol Acquisition Management IV LLC and updated beneficial ownership figures.

How many CTOS shares does Mark Ein now beneficially own?

He reports 5,159,319 shares beneficially owned, including options to purchase 20,000 shares that are currently exercisable.

What percentage of CTOS does this represent?

It represents 2.3% of the common stock, based on the disclosed outstanding share count.

What outstanding share count was used for the calculation?

The calculation uses 226,559,586 shares outstanding as of July 28, 2025, disclosed in the company’s Form 10‑Q filed July 30, 2025.

When did the in-kind distribution occur?

The distribution occurred on October 17, 2025.

Did the reporting persons remain above the 5% threshold?

No. The filing states the reporting persons have ceased to be beneficial owners of more than five percent of the class.

Which reporting persons now report zero CTOS shares?

Capitol Acquisition Management IV LLC, Capitol Acquisition Founder IV LLC, and Dyson Dryden each report 0 shares.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 10/21/2025 - 04:30 PM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

Custom Truck One Source, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

23204X103

(CUSIP Number)

Mark Ein
2200 Wilson Blvd, Suite 102 #447,
Arlington, VA, 22201
202-654-7001

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

10/17/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 23204X103

1

Name of reporting person

Capitol Acquisition Management IV LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC, OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 23204X103

1

Name of reporting person

Capitol Acquisition Founder IV LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC, OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 23204X103

1

Name of reporting person

Mark Ein

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 5,159,319.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 5,159,319.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

5,159,319.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

2.3 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 23204X103

1

Name of reporting person

Dyson Dryden

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock
(b)	Name of Issuer: Custom Truck One Source, Inc.
(c)	Address of Issuer's Principal Executive Offices: 7701 Independence Avenue, Kansas City, MISSOURI , 64125.
Item 1 Comment: This Amendment No. 1 to Schedule 13D (this "Amendment No. 1") amends and supplements the statement on Schedule 13D filed with the United States Securities and Exchange Commission on April 14, 2021 (the "Schedule 13D"), relating to the common stock, par value $0.0001 per share (the "Common Stock"), of Custom Truck One Source, Inc., a Delaware corporation (the "Issuer"), whose principal executive office is located at 7701 Independence Ave., Kansas City, MO 64125. Capitalized terms used herein without definition shall have the meaning set forth in the Schedule 13D.
Item 4.	Purpose of Transaction
	Item 4 of the Schedule 13D is hereby amended and supplemented with the following: Distribution In-Kind On October 17, 2025, Management IV distributed 3,670,279 shares of Common Stock to its members without consideration on a pro rata basis. As part of this distribution, Mr. Ein acquired 3,553,612 shares of Common Stock.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5 of the Schedule 13D is hereby amended and restated in its entirety as follows: The beneficial ownership set forth herein is based on 226,559,586 shares of Common Stock outstanding as of July 28, 2025, as disclosed in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on July 30, 2025.
(b)	Mr. Ein is the record holder of 5,139,319 shares of Common Stock and options to purchase 20,000 shares of Common Stock that are currently exercisable.
(c)	Other than as described in Item 4, the Reporting Persons have not effected any other transactions in Common Stock during the past 60 days.
(d)	None.
(e)	The Reporting Persons have ceased to be the beneficial owners of more than five percent of the outstanding Common Stock.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Capitol Acquisition Management IV LLC

Signature:	/s/ Mark Ein
Name/Title:	Mark Ein, Chief Executive Officer
Date:	10/21/2025

Capitol Acquisition Founder IV LLC

Signature:	/s/ Dyson Dryden
Name/Title:	Dyson Dryden, Chief Financial Officer
Date:	10/21/2025

Mark Ein

Signature:	/s/ Mark Ein
Name/Title:	Mark Ein
Date:	10/21/2025

Dyson Dryden

Signature:	/s/ Dyson Dryden
Name/Title:	Dyson Dryden
Date:	10/21/2025