Custom Truck One Source (CTOS) 10-Q 2021 Q1 Quarterly report

Exhibit 31.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER

PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Fred Ross, certify that:

1 I have reviewed the Quarterly Report on Form 10-Q of Custom Truck One Source, Inc. for the three months ended March 31, 2021;

2 Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3 Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of Custom Truck Once Source, Inc. as of, and for, the periods presented in this report;

4 Custom Truck One Source, Inc.’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for Custom Truck One Source, Inc. and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to Custom Truck Once Source, Inc., including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of Custom Truck Once Source, Inc.’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in Custom Truck Once Source, Inc.’s internal control over financial reporting that occurred during Custom Truck Once Source, Inc.’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5 Custom Truck Once Source, Inc.'s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the Custom Truck Once Source, Inc.'s auditors and the audit committee of the Custom Truck Once Source, Inc.’s board of directors:

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect Custom Truck Once Source, Inc.’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the Custom Truck Once Source, Inc.’s internal control over financial reporting.

Date:	May 17, 2021	/s/ Fred Ross
		Fred Ross
		Chief Executive Officer