This is Audit Analytics’ annual market share analysis of auditor engagements for public companies as of May 14, 2023. Using our Auditor Engagements data, we look at who is currently conducting audits of SEC public registrants, based on periodic reports filed with the SEC after March 1, 2022.
Audit firms are constantly competing to obtain public company clients. As of May 14, 2023, there were 258 firms conducting audits for 6,950 Securities and Exchange Commision (SEC) registrants. Continuing the upward trend seen in last year’s analysis, this represents a 4.5% increase in population. 2023 is the fourth year in a row we’ve observed an increase in SEC registrants.
The auditors with the most SEC registrant clients were EY, Deloitte, PwC, KPMG, Marcum, Grant Thornton, BDO, BF Borgers, Withum, and RSM. With a slight shift in order, the top ten firms by registrant count remain unchanged from the previous year.
The top ten firms collectively audit 68% of the total population. In comparison to our 2020, 2021, and 2022 analyses, this is the first year where the top ten audit firms remained static in terms of market concentration for SEC registrants. While the majority of the top ten firms managed to increase their clientele from 2022, Withum decreased in rank. They fell from sixth to ninth, auditing 177 clients in 2023 compared to 296 clients in 2022.
Market Share Analysis – Excluding Special Purpose Acquisition Companies (SPACs) 
As of May 14, 2023, there were 707 SPACs and shell companies registered with the SEC. These are entities with limited or no business operations. The emergence of SPACs and shell companies over the past few years has influenced audit market share.
When excluding SPACs, the top ten firms by registrant count changes. While the Big Four figures remain relatively unchanged, the smaller firms shift slightly. Most notably, the shifts in rank for Grant Thornton and Marcum when excluding SPACs.
Marcum’s concentration on SPACs accounts for 55% of their SEC registrant clients. When these companies are excluded, Marcum’s rank falls to sixth and Grant Thornton moves into fifth. Additionally, Withum no longer makes the list of top firms while Crowe moves into tenth.
Collectively, these top ten firms audit 69% of the public company market excluding SPACs.
Large-Accelerated Filer Market
Without a doubt, the Big Four firms dominated the market share of large-accelerated filers. Together, they audited 88% of this market. EY remained in the lead for a seventh consecutive year with 600 clients, auditing 28% of all large-accelerated filers.
Outside of the Big Four, there were 33 other firms that competed for the remaining 12% of the large-accelerated filer market.
Since last year’s analysis, the population of Large-Accelerated filers decreased by 4%.
Accelerated Filer Market
The Big Four along with Grant Thornton and BDO audited the greatest number of accelerated filers. Deloitte led this group with 148 clients and 19% of the market. Collectively, the top six firms constituted 72% of the accelerated filer market. There were 61 other firms who audited the remaining 214 companies.
The population of Accelerated filers increased 18% from last year.
Non-Accelerated Filer Market
The Big Four and Marcum account for 62% of the non-accelerated filer audit market. There were 74 other firms that shared the remaining 38% of non-accelerated filers.
While Deloitte led once again, PwC managed to take the lead over EY this year for second spot. PwC audited almost 40 more clients than their fellow Big Four associate and increased their market share by nearly three percentage points.
The population of Non-Accelerated filers increased 41% from last year.
Smaller Reporting Company Market
The audit firm market share of smaller reporting companies (SRC) is more diverse. There is significant competition among firms auditing smaller companies, with only 419 SRC registrants audited by 136 firms.
The top five firms, comprising only 26% of the SRC market in 2022, are BF Borgers, M&K CPAs, Gries & Associates, JP Centurion & Partners, and Victor Mokuolo CPA. Both Gries & Associates and Victor Mokuolo CPA succeeded in making the top five list after registering with the Public Company Accounting Oversight Board (PCAOB) back in 2021.
The remaining 74% of the market is audited by 131 other firms, of which 66 had only one SRC client.
The population of SRC filers decreased 16% from last year.
Non-Accelerated Filer and Smaller Reporting Company Market
Non-Accelerated Filer and Smaller Reporting Company (NAF & SRC) is the largest filer status population with nearly 3,000 registrants. The top six firms remained unchanged from last year, collectively auditing 40% of the market. The remaining 1,747 companies are shared among 192 other firms.
Marcum led this group with 448 clients and 15% of the market. This is mainly due to their concentration on SPACs, which constituted 63% of their NAF & SRC clients. In 2023, 91% of all SPACs and shell companies classified as a non-accelerated filer and smaller reporting company.
The population of non-accelerated filer and smaller reporting companies increased 5% from last year.
 For a complete analysis of audit firm market share excluding SPACs, access our report Who Audits Public Companies – 2023 Edition, here. The complete analysis includes registrant counts and market share for the top firms and additionally segments audit market by company size, market, jurisdiction, US region and industry. Refer to report for details of methodology.
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