The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until this Registration Statement shall become effective on such date as the SEC, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

This Amendment No. 1 to Registration Statement on Form S-3 (Registration Statement No. 333-259725) of the Registrant filed with the Securities and Exchange Commission on September 22, 2021 hereby amends the Registration Statement to increase the amount of securities to be registered and to provide for the resale of up to 207,745,626 shares of our common stock for the account of the selling security holders included herein and related disclosure of such holders.

The information contained in this prospectus is not complete and may be changed. Neither we nor theThe selling securityholders may not sell these securities until the Registration Statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not the solicitation of an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED MAY 6,SEPTEMBER 23, 2021

Prospectus

 Prospectus

Custom Truck One Source, Inc.

41,416,667207,745,626 Shares of Common Stock

(Consisting of 13,416,667 Shares of Common Stock Offered by Custom Truck One Source, Inc. and 28,000,000 Shares Offered by the Selling Securityholders)

This prospectus relates to (i) the resale of 28,000,000207,745,626 shares of Common Stock of Custom Truck One Source Inc., a Delaware corporation formerly known as Nesco Holdings, Inc. (“we,” “us,” “our” and the “Company”) issued in the PIPE Investment (as defined below), par value $0.0001 per share (the “Common Stock”) in connection with the (i) Common Stock issued to existing investors in Custom Truck One Source, L.P. in connection with the rollover of such entity, (ii) Common Stock held by certain qualified institutional buyers and accredited investors following the acquisition of NESCO Holdings, LP, a Delaware limited partnership, and NESCO Holdings I, Inc. by Capitol Investment Corp. IV and (iii) Common Stock issued by certain qualified institutional buyers and accredited investors in connection with the closing of the Acquisition (as defined below) by certain the selling securityholders (each a “selling securityholder” and, collectively, the “selling securityholders”) named in this prospectus from time to time in amounts, at prices and terms that will be determined at the time of the offering and (ii) the issuance by the Company of up to 13,416,667 sharesoffering. The registration of Common Stock issuable uponpursuant to this prospectus does not necessarily indicate a willingness on the exercise of warrants sold as part of the units in our initial public offering (“warrants”).selling securityholders to sell their shares.

On April 1, 2021 Custom Truck One Source, Inc., a Delaware corporation formerly known as Nesco Holdings, Inc., completed the acquisition (the “Acquisition”) of Custom Truck One Source, L.P. (“CTOS”) and its general partner pursuant to a Purchase and Sale Agreement entered into on December 3, 2020 (the “Purchase Agreement”) by and among NESCO Holdings II, Inc., certain affiliates of the Blackstone Group (“Blackstone”) and other direct and indirect equity holders (collectively, “Sellers”) of CTOS, Blackstone Capital Partners VI-NQ L.P. and, solely with respect to Section 9.04 of the Purchase Agreement, PE One Source Holdings, LLC, an affiliate of Platinum Equity. OnIn connection with the Closing of the Acquisition, certain of the selling stockholders received Common Stock of Custom Truck One Source Inc. in exchange for existing equity of Custom Truck One Source, L.P. In addition, on December 21,3, 2020, in connection with the entry into of the Purchase Agreement, the Company entered into subscription agreementsa common stock purchase agreement with PE One Source Holdings, LLC, one of the selling securityholders (the “Subscription Agreements”)stockholders, to finance, in part, the acquisition of CTOS. InAdditionally, certain of the selling stockholders received shares in connection with the closing of the Acquisition, the selling securityholders purchased the Common Stock at $5.00 per share for an aggregate purchase price of $140 million (the “PIPE Investment”). We are registering the resale of the Common Stock as required by the Subscription Agreements.Company’s initial formation transactions.

We will not receive any proceeds from the resale of the Common Stock by the selling securityholders. We will receive the proceeds from the cash exercise of the warrants, but not from any subsequent sale of the underlying shares of Common Stock by holders of the warrants. We will bear all costs, expenses and fees in connection with the registration of the Common Stock. We are registering the offering and sale of Common Stock by selling securityholders described herein to satisfy registration rights we have granted the selling securityholders in connection with the PIPE Investment pursuant to a registration rights agreementAmended and Restated Stockholders’ Agreement dated April 1, 20202021 (the “Registration Rights“Stockholders Agreement”).

This prospectus describes the general manner in which these securities may be offered and sold. If necessary, the issuance of Common Stockspecific manner in connectionwhich these securities may be offered and sold will be described in one or more supplements to this prospectus. Any prospectus supplement may add, update or change information contained in this prospectus. You should carefully read this prospectus and any applicable prospectus supplement, together with the warrants issueddocuments we incorporate by reference, before you invest in connection with theany of our initial public offering.securities.

The selling securityholders may offer and sell the Common Stock described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the Common Stock, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement, if any. The selling securityholders and any broker-dealer executing sell orders on behalf of the selling securityholders, may be deemed to be “underwriters” within the meaning of the Securities Act. Commissions received by any broker-dealer may be deemed to be underwriting commissions under the Securities Act. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and any prospectus supplement, if required.

Our Common Stock is listed on The New York Stock Exchange (“NYSE”) under the symbolssymbol “CTOS” and “CTOS.WS,” respectively.. On May 5,September 21, 2021, the closing price of our Common Stock was $10.55$9.45 per share.

Investing in our shares involves a number of risks. See “Risk Factors” on page 43 to read about factors you should consider before investing in our Common Stock.

Neither the SEC nor any state securities commission nor any other regulatory body has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is                , 2021.

TABLE OF CONTENTS

No one has been authorized to provide you with information that is different from that contained in this prospectus or any prospectus supplement. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus or any prospectus supplement. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the Common Stock to which they relate, nor do this prospectus and any accompanying prospectus supplement constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it unlawful to make such an offer or solicitation in such jurisdiction.

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the SEC using a “shelf” registration process. Under this shelf registration process, the selling securityholders may from time to time offer to sell shares of Common Stock described in this prospectus in one or more offerings. We may use this prospectus to sell up to an aggregate of 13,416,667 shares of Common Stock issuable upon exercise of the warrants from time to timeofferings as described in the section entitled “Plan of Distribution.”

This prospectus provides you with a general description of us and certain of our securities. We may also provide a prospectus supplement to add information to, or update or change information contained in, this prospectus. You should read both this prospectus and any applicable prospectus supplement together with the additional information to which we refer you in the sections of this prospectus entitled “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.”

You should assume that the information appearing in this prospectus and any applicable accompanying prospectus supplement is accurate as of the date on its respective cover, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

If the description of the offering varies between any prospectus supplement and this prospectus, you should rely on the information in any applicable prospectus supplement. Any statement made in this prospectus or in a document incorporated by reference in this prospectus will be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other subsequently filed document that is also incorporated by reference in this prospectus modifies or supersedes that statement. Any statement so modified or superseded will not, except as so modified or superseded, constitute a part of this prospectus. Before making an investment in any of our securities, you should carefully read this prospectus, any applicable prospectus supplement and any applicable free writing prospectus, together with the information incorporated and deemed to be incorporated by reference herein as described under “Incorporation of Certain Information by Reference” and the additional information described under the heading “Where You Can Find More Information.”

FORWARD-LOOKING STATEMENTS

Any statements made in this prospectus that are not statements of historical fact, including statements about our beliefs and expectations, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, and should be evaluated as such. Forward-looking statements include information concerning possible or assumed future results of operations, including descriptions of our business plan and strategies. These statements often include words such as “anticipate,” “expect,” “suggests,” “plan,” “believe,” “intend,” “estimates,” “targets,” “projects,” “should,” “could,” “would,” “may,” “will,” “forecast,” and other similar expressions. We base these forward-looking statements or projections on our current expectations, plans and assumptions that we have made in light of our experience in the industry, as well as our perceptions of historical trends, current conditions, expected future developments and other factors we believe are appropriate under the circumstances and at such time. As you read and consider this prospectus, you should understand that these statements are not guarantees of performance or results. The forward-looking statementsresults and projections are subject to and involve risks, uncertainties and assumptions and youassumptions. You should not place undue reliance on these forward-looking statements or projections.statements. Although we believe that these forward-looking statements and projections are based on reasonable assumptions at the time they are made, you should be aware that many factors could affect our actual financial results or results of operations and could cause actual results to differ materially from those expressed in the forward-looking statements and projections.statements. Below is a listsummary of risk factors applicable to us that may materially affect such forward-looking statements and projections:

These cautionary statements should not be construed by you to be exhaustive and are made only as of the date of this prospectus. We undertake no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, unless required by law. See “Risk Factors” in this prospectus for additional risks.

RISK FACTORS

An investment in our securities involves a high degree of risk. You should carefully consider the matters discussed under “Risk Factors” under in our Annual Report on Form 10-K, filed with the SEC on March 9, 2021, as updated by our subsequent Quarterly Reports on Form 10-Q, and in the Acquisition Proxy Statement. You should also carefully consider the matters discussed under “Risk Factors” or any similar caption in other documents or reports that we file with the SEC that are incorporated or deemed to be incorporated by reference in this prospectus as well as any risks described in any applicable prospectus supplement or free writing prospectus that we provide you in connection with an offering of securities pursuant to this prospectus. See “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.” Additionally, the risks and uncertainties discussed in this prospectus or in any document incorporated by reference into this prospectus are not the only risks and uncertainties that we face, and our business, financial condition, prospects, results of operations, cash flow and the market price of our securities could be materially adversely affected by other matters that are not known to us or that we currently do not consider to be material.

USE OF PROCEEDS

We will receive up to an aggregate of approximately $154.3 million from the exercise of the warrants, assuming the exercise in full of all the warrants for cash. We expect to use the net proceeds from the exercise of the warrants for general corporate purposes.

We will not receive any of the proceeds from the sale of Common Stock covered by this prospectus. The selling securityholders will receive all of the proceeds from the offering of Common Stock.

The selling securityholders will pay any underwriting discounts and commissions and expenses incurred by the selling securityholders for brokerage, accounting, tax or legal services or any other expenses incurred by the selling securityholders in disposing of the shares. We will bear all other costs, fees and expenses incurred in effecting the registration of the shares covered by this prospectus, including, without limitation, all registration and filing fees, fees and expenses of our counsel, certain expenses of counsel to the selling securityholders and our independent registered public accountants.

SELLING SECURITYHOLDERS

This prospectus relates to the resale of up to 28,000,000207,745,626 shares of our Common Stock issuedin connection with Blackstone’s registration rights pursuant to the PIPE InvestmentStockholders’ Agreement, including additional shares of Common Stock held by certain ofsecurityholders that have certain rights to piggyback registration under the selling securityholders named herein (the “PIPE Investors”).Stockholders Agreement. The selling securityholders may from time to time offer and sell any or all of the shares of Common Stock set forth below pursuant to this prospectus and any accompanying prospectus supplement.supplement, as well as certain other of our stockholders.

When we refer to the “selling securityholders” in this prospectus, we mean the persons listed in the table below, and the pledgees, donees, transferees, assignees, successors, designees and others who later come to hold any of the selling securityholders’ interest in the Common Stock other than through a public sale.

The following table set forth, as of the date of this prospectus, the names of the selling securityholders, the beneficial ownership of Common Stock held by each selling securityholder, the aggregate amount of Common Stock that the selling securityholders may offer pursuant to this prospectus and the number and percentage of shares of Common Stock that each selling securityholder will beneficially own after this offering assuming they sell all such securities that they may offer pursuant to this prospectus. The percentage of shares of Common Stock owned by the selling securityholders following the offering of any shares of Common Stock pursuant to this prospectus, is based on 245,919,383245,919,185 shares of Common Stock and 20,949,980 warrants outstanding as of April 30,August 31, 2021. Derivative securities exercisable or convertible into shares of our Common Stock within sixty (60) days of the date hereof are deemed to be beneficially owned and outstanding for computing the share ownership and percentage of the person holding securities, but are not deemed outstanding for computing the percentage of any other person. Unless otherwise indicated, the we believe that all persons named in the tables have sole voting and investment power with respect to all shares of Common Stock beneficially owned by them.

Information with respect to beneficial ownership is based on information obtained from such selling securityholder and publicly available information. Information with respect to shares beneficially owned after the offering assumes the sale of all the shares offered and no other purchases or sales of Common Stock. Information about other selling securityholders, if any, including their identities, the Common Stock to be registered on their behalf and the amounts to be sold by them, will be set forth in a prospectus supplement.

To the extent permitted by law, a prospectus supplement may add, update, substitute or change the information contained in this prospectus, including the identity of each selling securityholders and the number of shares of Common Stock registered on its behalf. A selling securityholder may sell or otherwise transfer all, some or none of such shares of Common Stock in this offering. See “Plan of Distribution.”

DESCRIPTION OF SECURITIES

The following summary of our capital stock and our charter and our bylaws does not purport to be complete and is qualified in its entirety by reference to the provisions of applicable law and to our charter and bylaws, which are filed as exhibits to the Registration Statement of which this prospectus is a part.

General

We are a Delaware corporation. Our charter provides for 500,000,000 authorized shares of Common Stock and 10,000,000 authorized shares of preferred stock. As of April 30,August 31, 2021, there were 245,919,383245,919,185 shares of Common Stock, no shares of preferred stock and 20,949,980 warrants to purchase shares of our Common Stock outstanding.

Common Stock

The holders of Common Stock are entitled to one vote for each share held of record on all matters to be voted on by stockholders.

Holders of Common Stock do not have any conversion, preemptive or other subscription rights and there will be no sinking fund or redemption provisions applicable to the Common Stock.

The rights, preferences and privileges of the holders of Common Stock are subject to those of the holders of any shares of preferred stock we may issue in the future.

Voting Rights

Each holder of our Common Stock is entitled to one vote per share on each matter submitted to a vote of stockholders, unless otherwise provided by our certificate of incorporation. Our bylaws provide that the presence, in person or by proxy, of holders of shares representing a majority of the issued and outstanding shares of capital stock entitled to vote at a stockholders’ meeting shall constitute a quorum. When a quorum is present, the affirmative vote of a majority of the votes cast is required to take action, unless otherwise specified by law, our bylaws, our certificate of incorporation or our Amended and Restated Stockholders’ Agreement, dated as of April 1, 2021.Agreement. There are no cumulative voting rights.

Dividend Rights

Each holder of shares of our capital stock is entitled to receive such dividends and other distributions in cash, stock or property as may be declared by our board of directors from time to time out of our assets or funds legally available for dividends or other distributions. These rights are subject to the preferential rights of the holders of our preferred stock, if any, and any contractual limitations on our ability to declare and pay dividends.

Liquidation Rights

If the Company is involved in a consolidation, merger, recapitalization, reorganization, voluntary or involuntary liquidation, dissolution or winding up of affairs, or similar event, each holder of Common Stock will participate pro rata in all assets remaining after payment of liabilities, subject to prior distribution rights of preferred stock, if any, then outstanding.

Transfer Agent and Registrar

The transfer agent and registrar for our Common Stock is Continental Stock Transfer & Trust Company, 1 State Street, 30th Floor, New York, New York 10004.

Listing

Our Common Stock is listed on the New York Stock Exchange under the symbol “CTOS”.

Certain Anti-Takeover Provisions of Delaware Law and Our Certificate of Incorporation

We have certain anti-takeover provisions in place as follows:

Staggered Board of Directors

Our charter provides that the board be classified into three classes of directors of approximately equal size. As a result, in most circumstances, a person can gain control of our board only by successfully engaging in a proxy contest at two or more annual meetings. Furthermore, because the board is classified, directors may be removed only with cause by a majority of our outstanding shares.

Action by Written Consent; Special meeting of stockholders

Our charter provides that stockholder action may only be taken by written consent in lieu of a meeting while Platinum Equity Advisors, LLC (“Platinum”) and its affiliates collectively beneficially own, in the aggregate, at least 50% in voting power of the stock of the Company entitled to vote generally in the election of directors, any action required or permitted to be taken at any annual or special meeting of stockholders of the Company.

The General Corporation Law of the State of Delaware (the “DGCL”) provides that special meetings of our stockholders may be called by the board of directors. Our charter provides that, at any time when Platinum and its affiliates collectively beneficially own, in the aggregate, at least 5% in voting power of the stock of the Company entitled to vote generally in the election of directors, the Chairman of the Board shall call a special meeting of stockholders at the request of Platinum from time to time.

Advance Notice Requirements for Stockholder Proposals and Director Nominations

Our bylaws provide that stockholders seeking to bring business before our annual meeting of stockholders, or to nominate candidates for election as directors at our annual meeting of stockholders, must provide timely notice of their intent in writing. To be timely, a stockholder’s notice will need to be received by the company secretary at our principal executive offices not later than the close of business on the 90th day nor earlier than the open of business on the 120th day prior to the anniversary date of the immediately preceding general meeting of stockholders (except that, with respect to Platinum’s nomination of directors, the reference to 90 days shall be 45 days). Such notice also must fulfill certain information requirements with respect to the stockholder delivering such notice and the matter proposed (or director candidate nominated) of which Platinum is partially exempt. Pursuant to Rule 14a-8 of the Exchange Act, proposals seeking inclusion in our annual proxy statement must comply with the notice periods contained therein. Our bylaws also specify certain requirements as to the form and content of a stockholders’ meeting. These provisions may preclude our stockholders from bringing matters before the general meeting of stockholders or from making nominations for directors at our general meeting of stockholders.

Authorized but Unissued Shares

Our authorized but unissued Common Stock and preferred stock will be available for future issuances without stockholder approval and could be utilized for a variety of corporate purposes, including future offerings to raise additional capital, acquisitions and employee benefit plans. The existence of authorized but unissued and unreserved Common Stock and preferred stock could render more difficult or discourage an attempt to obtain control of the Company by means of a proxy contest, tender offer, merger or otherwise.

Exclusive Forum Selection

Our certificate of incorporation requires, to the fullest extent permitted by law, that, unless we consent in writing to the selection of an alternative forum, derivative actions brought in our name, actions against directors, officers and employees for breach of fiduciary duty and other similar actions may be brought only in the Court of Chancery in the State of Delaware (or, in the event that the Court of Chancery of the State of Delaware does not have jurisdiction (such as in the case of claims brought to enforce any liability or duty created by the Exchange Act, in which case federal courts have exclusive jurisdiction), the federal district court for the District of Delaware or other state courts of the State of Delaware) and, if brought outside of Delaware, the stockholder bringing the suit will be deemed to have consented to service of process on such stockholder’s counsel. This exclusive forum provision applies to state and federal law claims brought by stockholders (including claims pursuant to the Securities Act and the Exchange Act), although stockholders will not be deemed to have waived the Company’s compliance with the federal securities laws and the rules and regulations thereunder. The enforceability of similar choice of forum provisions in other companies’ organizational documents has been challenged in legal proceedings, and it is possible that, in connection with claims arising under federal securities laws, a court could find the choice of forum provisions contained in our charter to be inapplicable or unenforceable. Although we believe this provision benefits our company by providing increased consistency in the application of Delaware law in the types of lawsuits to which it applies, the provision may have the effect of discouraging lawsuits against our directors and officers.

Business Combinations with Interested Stockholders

Our charter provides that we are not subject to Section 203 of the DGCL, an anti-takeover law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a business combination, such as a merger, with an “interested stockholder” (which includes a person or group owning 15% or more of the corporation’s voting stock) for a period of three years following the date the person became an interested stockholder, unless (with certain exceptions) the business combination or the transaction in which the person became an interested stockholder is approved in a prescribed manner. Accordingly, we are not subject to any anti-takeover effects of Section 203. Nevertheless, our charter will contain provisions that will have a similar effect to Section 203, except that they will provide that (i) Platinum; (ii) Energy Capital Partners, LLC, a Delaware limited liability company, Energy Capital Partners II, LLC, Energy Capital Partners III, LLC, Energy Capital Partners Mezzanine, LLC, Energy Capital Partners IV, LLC, Energy Capital Partners Credit Solutions II, LLC, ECP ControlCo, LLC, Energy Capital Partners Holdings, LP, ECP Feeder, LP, and ECP Management GP, LLC; (iii) Capitol Acquisition Management IV LLC and Capitol Acquisition Founder IV LLC; and (iv) Blackstone Management Partners L.L.C. and their respective direct and indirect transferees will not be deemed to be “interested stockholders,” regardless of the percentage of the Company’s voting stock owned by them, and accordingly will not be subject to such restrictions.

Limitation on Liability and Indemnification of Directors and Officers

Our charter provides that directors and officers will be indemnified by us to the fullest extent authorized by Delaware law as it now exists or may in the future be amended. In addition, our charter provides that directors will not be personally liable for monetary damages to the Company for breaches of their fiduciary duty as directors, unless they violated their duty of loyalty to the Company or its stockholders, acted in bad faith, knowingly or intentionally violated the law, authorized unlawful payments of dividends, unlawful stock purchases or unlawful redemptions, or derived an improper personal benefit from their actions as directors.

Our bylaws also permit the Company to secure insurance on behalf of any officer, director or employee for any liability arising out of his or her actions, regardless of whether Delaware law would permit indemnification. We have purchased a policy of directors’ and officers’ liability insurance that insures its directors and officers against the cost of defense, settlement or payment of a judgment in some circumstances and insures it against the obligations to indemnify the directors and officers.

These provisions may discourage stockholders from bringing a lawsuit against our directors for breach of their fiduciary duty. These provisions also may have the effect of reducing the likelihood of derivative litigation against directors and officers, even though such an action, if successful, might otherwise benefit the Company and its stockholders. Furthermore, a stockholder’s investment may be adversely affected to the extent the Company pays the costs of settlement and damage awards against directors and officers pursuant to these indemnification provisions. We believe that these provisions, the insurance and the indemnity agreements are necessary to attract and retain talented and experienced directors and officers.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, we have been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

PLAN OF DISTRIBUTION

We are registering the issuance of 13,416,667 shares of Common Stock issuable upon exercise of warrants that were issued in connection with our initial public offering. We are also registering the resale by the selling securityholders of up to 28,000,000 shares of Common Stock issue in connection with the closing of the Acquisition and concurrently therewith. The selling securityholders includingand any of their pledgees, donees, assignees, transferees assignees and others who later comesuccessors-in interest may, from time to holdtime, sell, transfer, or otherwise dispose of. separately or together, some or all of the shares of Common Stocksecurities covered by this prospectus may from time to time offer some or all ofon the shares of Common Stock covered by this prospectus. To the extent required, this prospectus may be amended and supplemented from time to time to describe a specific plan of distribution.

The selling securityholders will not pay any of the costs, expenses and fees in connection with the registration and sale of the shares of Common Stock covered by this prospectus, but they will pay any and all underwriting discounts, selling commissions and similar charges attributable to sales of Common Stock. We will not receive any proceeds from the sale of the shares of our Common Stock covered hereby but we will receive the exercise price of the warrants. The selling securityholders may sell the shares of Common Stock covered by this prospectus from time to time, and may also decide not to sell allNYSE or any ofother stock exchange, market or trading facility on which the shares of Common Stock that theysecurities are allowed to sell under this prospectus. The selling securityholders will act independently of ustraded, listed or quoted in making decisions regarding the timing, manner and size of each sale.over-the-counter market or in private transactions. These dispositionssales may be at fixed prices, at prevailing market prices prevailing at the time of sale, at prices related to suchthe prevailing market prices,price, at varying prices determined at the time of sale, or at privately negotiated prices. Sales may be made byTo the extent the selling securityholders gift, pledge or otherwise transfer the securities offered hereby, such transferees may offer and sell the securities from time to time under this prospectus, provided that, if required under the Securities Act, and the rules and regulations promulgated thereunder, this prospectus has been amended under Rule 424(b)(3) or other applicable provision of the Securities Act, to include the name of such transferee in the list of selling securityholders under this prospectus. Subject to compliance with applicable law, we and the selling securityholders may use any one or more types of transactions, which may include:the following methods when selling securities:

AWe have not, and to our knowledge, the selling securityholdersecurityholders have not, entered into any agreements, understandings or arrangements with any underwriters or broker-dealers regarding the sale of the securities covered by this prospectus. At any time a particular offer of the securities covered by this prospectus is made, a revised prospectus or prospectus supplement, if required, will set forth the aggregate amount of securities covered by this prospectus being offered and the terms of the offering, including the name or names of any underwriters, dealers, brokers or agents. In addition, to the extent required, any discounts, commissions, concessions and other items constituting underwriters’ or agents’ compensation, as well as any discounts, commissions or concessions allowed or reallowed or paid to dealers, will be set forth in such revised prospectus or prospectus supplement. Any such required prospectus supplement, and, if necessary, a post-effective amendment to the registration statement of which this prospectus is a part, will be filed with the SEC to reflect the disclosure of additional information with respect to the distribution of the securities covered by this prospectus.

To the extent required, any applicable prospectus supplement will set forth whether or not underwriters may over-allot or effect transactions that stabilize, maintain or otherwise affect the market price of the securities at levels above those that might otherwise prevail in the open market, including, for example, by entering stabilizing bids, effecting syndicate covering transactions or imposing penalty bids. The selling securityholders may also resell all or a portion of itssell shares of Common Stock in open market transactions in reliance uponour securities under Rule 144 under the Securities Act, provided it meetsif available, or in other transactions exempt from registration, rather than under this prospectus. The selling securityholders have the criteriasole and conformsabsolute discretion not to accept any purchase offer or make any sale of securities. Broker-dealers engaged by us or the requirementsselling securityholders may arrange for other broker-dealers to participate in sales. If the selling securityholders effect such transactions by selling securities to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of Rule 144.

Thediscounts, concessions or commissions from the selling securityholders (and/or, if any broker-dealer acts as agent for the purchaser of the securities, from the purchaser) in amounts to be negotiated. In connection with the sale of securities, the selling securityholders may enter into sale, forward-sale and derivative transactions with third parties, or may sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those sale, forward-sale or derivative transactions, the third parties may sell securities covered by this prospectus or the applicable prospectus supplement, including in short sale transactions and by issuing securities that are not covered by this prospectus but are exchangeable for or represent beneficial interests in the Common Stock. The third parties also may use shares received under those sale, forward-sale or derivative arrangements or shares pledged by the selling securityholder or borrowed from the selling securityholders or others to settle such third-party sales or to close out any related open borrowings of shares of Common Stock. The third parties may deliver this prospectus in connection with any such transactions. Any third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement (or a post-effective amendment to the Registration Statement of which this prospectus is a part).

In addition, the selling securityholders may engage in hedging transactions with broker-dealers or other financial institutions, which may in connection with distributions of shares of Common Stock or otherwise. In those transactions, broker-dealers mayturn engage in short sales of the securities in the course of hedging the positions they assume with selling securityholders.assume. The selling securityholders may also sell securities short after the effective date of the registration statement of which this prospectus is a part and redeliverdeliver these securities to close out suchtheir short positions.positions, or loan or pledge securities to broker-dealers that in turn may sell these securities. The selling securityholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of securities to the broker-dealer. Theoffered by this prospectus, which securities such broker-dealer or other financial institution may then resell or otherwise transfer such securities pursuant to this prospectus. prospectus (as supplemented or amended to reflect such transaction).

The selling securityholders also may loan or pledge shares,act independently of us in making decisions with respect to the price, timing, manner and the borrower or pledgee may sell or otherwise transfer the Common Stock so loaned or pledged pursuant to this prospectus. Such borrower or pledgee also may transfer those sharessize of Common Stock to investors in our securities or the selling securityholders’ securities or in connection with the offering of other securities not covered by this prospectus.

To the extent necessary, we may amend or supplement this prospectus from time to time to describe a specific plan of distribution. We will file a supplement to this prospectus, if required, upon being notified by the selling securityholders that any material arrangement has been entered into with a broker-dealer for theeach sale of shares through a block trade, offering or asecurities. Offers to purchase by a broker or dealer. The applicable prospectus supplement will set forth the specific terms of the offering of securities including:

In connection with sales of shares of Common Stock covered hereby, the selling securityholders and any underwriter, broker-dealer or agent and any other participating broker-dealer that executes sales for the selling securityholders may be deemed to be an “underwriter” within the meaning of the Securities Act. Accordingly, any profits realizedsolicited directly by the selling securityholders and any compensation earned by such underwriter, broker-dealer or agentthe sale thereof may be deemedmade by the selling securityholders directly to institutional investors or others. In such a case, no underwriters or agents would be underwriting discountsinvolved. The selling securityholders may use electronic media, including the Internet, to sell offered securities directly. The selling stockholders may offer the securities covered by this prospectus into an existing trading market on the terms described in the prospectus supplement relating thereto. Underwriters, dealers and commissions. Becauseagents who participate in any at-the-market offerings will be described in the prospectus supplement relating thereto. The terms of each such agreement will be set forth in more detail in the applicable prospectus supplement. The selling securityholders may sell the securities through agents from time to time. Generally, any agent will be acting on a best efforts basis for the period of its appointment. If the selling securityholders utilize a dealer in the sale of the securities in respect of which this prospectus is delivered, the selling securityholder may be deemedsell such securities to the dealer, as principal. The dealer may then resell such securities to the public at varying prices to be “underwriters” under the Securities Act, the selling securityholders must deliver this prospectus and any prospectus supplement in the manner requireddetermined by the Securities Act. This prospectus delivery requirement may be satisfied throughdealer at the facilitiestime of the New York Stock Exchange in accordance with Rule 153 under the Securities Act.

We and the selling securityholders have agreed to indemnify each other against certain liabilities, including liabilities under the Securities Act. In addition, we or the selling securityholders may agree to indemnify any underwriters, broker-dealers and agents against or contribute to any payments the underwriters, broker-dealers or agents may be required to make with respect to, civil liabilities, including liabilities under the Securities Act. Underwriters, broker-dealers and agents and their affiliates are permitted to be customers of, engage in transactions with, or perform services for us and our affiliates or the selling securityholders or their affiliates in the ordinary course of business.resale.

The selling securityholders may from time to time pledge or grant a security interest in some or all of their securities to their broker-dealers under the margin provisions of customer agreements or to other parties to secure other obligations. If a selling securityholder defaults on a margin loan or other secured obligation, the broker-dealer or secured party may, from time to time, offer and sell the securities pledged or secured thereby pursuant to this prospectus or, to the extent required under the applicable securities laws, under an amendment to this prospectus under Rule 424 or other applicable provision of the Securities Act. The selling securityholders and any other persons participating in the sale or distribution of the securities will be subject to applicable provisions of Regulation M ofthe Securities Act and the Exchange Act, and the rules and regulations thereunder, whichincluding, without limitation, Regulation M. These provisions may restrict certain activities of, and limit the timing of purchases and sales of any of the Common Stocksecurities by, the selling securityholders. Regulation M may also restrict the ability ofsecurityholders or any other person, engaged in the distribution of shares of Common Stock to engage in market-making activities with respect to the shares of Common Stock. These restrictionswhich limitations may affect the marketability of such shares of Common Stock.

In order to comply with applicable securities laws of some states,the securities. The selling securityholders also may transfer the shares of Common Stockour securities in other circumstances, in which case the transferees, pledgees or other successors-in-interest will be the selling beneficial owners for purposes of this prospectus. A selling securityholder that is an entity may elect to make an in-kind distribution of securities to its members, partners or shareholders pursuant to the registration statement of which this prospectus is a part by delivering a prospectus. To the extent that such members, partners or shareholders are not affiliates of ours, such members, partners or shareholders would thereby receive freely tradeable securities pursuant to the distribution through a registration statement.

If the selling securityholders use one or more underwriters in the sale, the underwriters will acquire the securities for their own account, and they may resell these securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The securities may be offered and sold to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more of such firms. The selling securityholders and any broker-dealers or agents that are involved in those jurisdictions only through registeredselling the securities may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. In such event, any commissions received by such broker-dealers or licensed brokersagents and any profit on the resale of the securities purchased by them may be deemed to be underwriting commissions or dealers. In addition, in certain statesdiscounts under the Securities Act. Underwriters may resell the shares of Common Stockto or through dealers, and those dealers may not be sold unless they have been registered or qualified for salereceive compensation in the applicable stateform of one or an exemptionmore discounts, concessions or commissions from the registration or qualification requirements is available. In addition, any shares of Common Stock of aunderwriters and commissions from purchasers for which they may act as agents. We have not, and to our knowledge, the selling securityholders covered by this prospectus that qualify for sale pursuanthave not, entered into any agreement or understanding, directly or indirectly, with any person to Rule 144distribute the securities offered hereby.

We are required to pay all fees and expenses incident to the registration of our securities. We have agreed to indemnify the selling securityholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act. We and the selling securityholders may agree to indemnify underwriters, broker-dealers or agents against certain liabilities, including liabilities under the Securities Act, and may also agree to contribute to payments which the underwriters, broker-dealers or agents may be sold in open market transactions under Rule 144 rather thanrequired to make. We have also agreed to keep the registration statement of which this prospectus forms a part effective until the selling securityholders have disposed of all of the secondary securities covered by this prospectus.

There can be no assurance that we or any selling securityholder will sell, nor are we or any selling securityholder required to sell, any or all of the securities registered pursuant to the registration statement of which this prospectus.prospectus is a part.

To the extent required, this prospectus may be amended and/or supplemented from time to time to describe a specific plan of distribution.

If required, we may add transferees, successors and donees by prospectus supplement in instances where the transferee, successor or donee has acquired its shares from holders named in this prospectus after the effective date of this prospectus. Transferees, successors and donees of identified selling securityholders may not be able to use this prospectus for resales until they are named in the selling securityholders table by prospectus supplement or post-effective amendment. See “Selling Securityholders.”

LEGAL MATTERS

Latham & Watkins, LLP, Washington, D.C. will pass upon the validity of the Common Stock offered hereby on our behalf.hereby. Any underwriters or agents will be advised about other issues relating to the offering by counsel to be named in the applicable prospectus supplement.

EXPERTS

The consolidated financial statements and the related financial statement schedule of Nesco Holdings, Inc. incorporated in this prospectus by reference from the Company's Annual Report on Form 10-K for the year ended December 31, 2020, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements and financial statement schedule have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

The consolidated financial statements of Custom Truck One Source, L.P. and subsidiaries as of December 31, 2020 and 2019, and for the three years ended December 31, 2020, 2019 and 2018, incorporated in this prospectus by reference, have been audited by Deloitte & Touche LLP, independent auditors, as stated in their report incorporated herein by reference, and have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

The Company files annual, quarterly and current reports, proxy statements and other information with the SEC. The SEC also maintains an Internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC. The address of that site is www.sec.gov.

Our website is located at https://customtruck.com, and our investor relations website is located at https://investors.customtruck.com. The information posted on our website is not incorporated into this prospectus. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to reports filed or furnished pursuant to Sections 13(a) and 15(d) of the Exchange Act, are available free of charge on our investor relations website as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. You may also access all of our public filings through the SEC’s website at www.sec.gov. Investors and other interested parties should note that we use our investor relations website to publish important information about us, including information that may be deemed material to investors. We encourage investors and other interested parties to review the information we may publish through our investor relations website, in addition to our SEC filings, press releases, conference calls, and webcasts.

The Registration Statement containing this prospectus, including exhibits to the Registration Statement, provides additional information about us and the Common Stock offered under this prospectus. The Registration Statement can be read at the SEC website.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” information into this prospectus, which means that we can disclose important information about us by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be a part of this prospectus. This prospectus incorporates by reference the documents and reports listed below (other than portions of these documents that are either (1) described in paragraph (e) of Item 201 of Regulation S-K or paragraphs (d)(1)-(3) and (e)(5) of Item 407 of Regulation S-K promulgated by the SEC or (2) deemed to have been furnished and not filed in accordance with SEC rules, including Current Reports on Form 8-K furnished under Item 2.02 or Item 7.01 (including any financial statements or exhibits relating thereto furnished pursuant to Item 9.01), unless otherwise indicated therein):

We also incorporate by reference the information contained in all other documents we file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (other than portions of these documents that are either (1) described in paragraph (e) of Item 201 of Regulation S-K or paragraphs (d)(1)-(3) and (e)(5) of Item 407 of Regulation S-K promulgated by the SEC or (2) deemed to have been furnished and not filed in accordance with SEC rules, including Current Reports on Form 8-K furnished under Item 2.02 or Item 7.01 (including any financial statements or exhibits relating thereto furnished pursuant to Item 9.01, unless otherwise indicated therein)) after the initial filing of the Registration Statement of which this prospectus forms a part and prior to the completion of the offering of all securities covered by this prospectus and any accompanying prospectus supplement. The information contained in any such document will be considered part of this prospectus from the date the document is filed with the SEC.

If you make a request for such information in writing or by telephone, we will provide you, without charge, a copy of any or all of the information incorporated by reference into this prospectus. Any such request should be directed to:

7701 Independence Ave

Kansas City, Missouri 64125

(816) 241-4888

Attention: Bradley Meader

You should rely only on the information contained in, or incorporated by reference into, this prospectus, in any accompanying prospectus supplement or in any free writing prospectus filed by us with the SEC. We have not authorized anyone to provide you with different or additional information. You should not assume that the information in this prospectus or in any document incorporated by reference is accurate as of any date other than the date on the front cover of the applicable document.

Custom Truck One Source, Inc.

41,416,667207,745,626 Shares of Common Stock

(Consisting of 13,416,667 Shares of Common Stock Offered by Custom Truck One Source, Inc. and 28,000,000 Shares Offered by the Selling Securityholders)

PROSPECTUS

PROSPECTUS

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth the various expenses expected to be incurred by the Company in connection with the sale and distribution of the securities being registered hereby, other than underwriting discounts and commissions. All amounts are estimated except the SEC registration fee SEC registration fee.

Item 15. Indemnification of Directors and Officers

Subsection (a) of Section 145 of the General Corporation Law of the DGCL empowers a corporation to indemnify any person who was or is a party or who is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that the person is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe the person’s conduct was unlawful.

Subsection (b) of Section 145 empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that the person acted in any of the capacities set forth above, against expenses (including attorneys’ fees) actually and reasonably incurred by the person in connection with the defense or settlement of such action or suit if the person acted in good faith and in a manner the person reasonably believed to be in or not opposed to the best interests of the corporation, except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or the court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery or such other court shall deem proper.

Section 145 further provides that to the extent a director or officer of a corporation has been successful on the merits or otherwise in the defense of any action, suit or proceeding referred to in subsections (a) and (b) of Section 145, or in defense of any claim, issue or matter therein, such person shall be indemnified against expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection therewith; that indemnification provided for by Section 145 shall not be deemed exclusive of any other rights to which the indemnified party may be entitled; and the indemnification provided for by Section 145 shall, unless otherwise provided when authorized or ratified, continue as to a person who has ceased to be a director, officer, employee or agent and shall inure to the benefit of such person’s heirs, executors and administrators. Section 145 also empowers the corporation to purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise against any liability asserted against such person and incurred by such person in any such capacity, or arising out of his status as such, whether or not the corporation would have the power to indemnify such person against such liabilities under Section 145.

Section 102(b)(7) of the DGCL provides that a corporation’s certificate of incorporation may contain a provision eliminating or limiting the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, provided that such provision shall not eliminate or limit the liability of a director (i) for any breach of the director’s duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL or (iv) for any transaction from which the director derived an improper personal benefit.

The Company’s certificate of incorporation provides that to the fullest extent permitted by the DGCL, a director of the Company shall not be personally liable to the Company or its stockholders for monetary damages for breach of fiduciary duty as a director. The Company’s bylaws provide that to the fullest extent permitted by applicable law as it presently exists or may hereafter be amended, any person who was or is made or is threatened to be made a party or is otherwise involved in any action, suit or proceeding, whether civil, criminal administrative or investigative (a “Proceeding”), by reason of the fact that the person is the legal representative, is or was a director or officer of the corporation or while serving as a director or officer of the Company, is or was serving at the request of the Company as a director, officer, employee or agent of another corporation or of a partnership, joint venture, trust, enterprise or non-profit entity, including service with respect to employee benefit plans, against all liability and loss suffered and expenses (including attorneys’ fee, judgments, fines, ERISA excise taxes or penalties and amounts paid in settlement) reasonably incurred by such person in connection with any such Proceeding. With respect to any such Proceeding initiated by any such indemnified person, the Company will be required to indemnity such person only if the Proceeding was authorized in the specific case by the board of directors of the Company.

The Company entered into indemnification agreements with its directors and executive officers, in addition to the indemnification provided for in its certificate of incorporation and bylaws, and intends to enter into indemnification agreements with any new directors and executive officers in the future.

The Company has purchased and intends to maintain insurance on behalf of any person who is or was a director or officer of the Company against any loss arising from any claim asserted against him or her and incurred by him or her in any such capacity, subject to certain inclusions.

Pursuant to the Agreement and Plan of Merger, dated as of April 7, 2019 (as amended, the “Merger Agreement”), pursuant to which NESCO Holdings I, Inc. became a wholly owned subsidiary of the Company, from and after July 31, 2019 (the “Effective Time”), the Company and Capitol Investment Merger Sub 2, LLC, a wholly owned subsidiary of the Company, are required to indemnify and hold harmless each director as of the Effective Time and former director and officer of Nesco Holdings I, Inc. and the Company, and their respective subsidiaries against any costs or expenses (including reasonable attorneys’ fees), judgments, fines, losses, claims, damages or liabilities incurred in connection with any claim, action, suit, assessment, arbitration, proceeding or investigation, in each case that is by or before any federal, state, provincial, municipal, local or foreign government, government authority, regulatory or administrative agency, governmental commission, department, board, bureau, agency or instrumentality, court or tribunal, or arbitrator, whether civil, criminal, administrative or investigative, arising out of or pertaining to matters existing or occurring at or prior to the Effective Time, whether asserted or claimed prior to, at or after the Effective Time, to the fullest extent such entities or their subsidiaries, as the case may be, would have been permitted under applicable law and its respective certificate of incorporation, certificate of formation, bylaws, limited liability company agreement or other organizational documents in effect on the date of the Merger Agreement to indemnify such person (including the advancing of expenses as incurred to the fullest extent permitted under applicable law). In addition, pursuant to the Merger Agreement, the Company shall, and shall cause Capitol Investment Merger Sub 2, LLC and its subsidiaries to (i) maintain until July 31, 2025 provisions in their respective certificate of incorporation, certificate formation, bylaws, limited liability company agreement and other organizational documents concerning the indemnification and exoneration (including provisions relating to expense advancement) of such entities’ officers, directors, employees, and agents that are no less favorable that the provisions in such documents applicable as of the date of the Merger Agreement and (ii) not amend, repeal or otherwise modify such provisions in any respect that would adversely affect the rights of such indemnified persons, except as required by law.

Furthermore, pursuant to the Merger Agreement, the Company is required to maintain until July 31, 2025, effective directors’ and officers’ liability insurance covering individuals that were covered by Nesco Holdings I, Inc.’s and its subsidiaries’ directors’ and officers’ liability insurance policies as of the date of the Merger Agreement, on terms not less favorable than the terms of such existing policies, subject to certain limitations. In addition, prior to the Effective Time, the Company purchased a six-year prepaid “tail policy” for the non-cancellable extension of the directors’ and officers’ liability coverage of the Company’s then existing directors’ and officers’ insurance policies for a claims reporting or discovery period of at least six years from and after the Effective Time with respect to any claim related to any period of time at or prior to the Effective Time of the merger.

The above discussion of Section 145 of the DGCL, the Company’s Certificate of Incorporation, the Company’s Bylaws and the applicable provisions of the Merger Agreement is not intended to be exhaustive and is respectively qualified in its entirety by Section 145 of the DGCL, the Company’s Certificate of Incorporation, the Company’s Bylaws and the Merger Agreement.

Item 16. Exhibits

(a) Exhibits