After losing market share for public company audits in 2024, the Big Four accounting firms held steady in 2025, accounting for just over half (51%), according to a new report.
Overall, the distribution of Securities and Exchange Commission audit clients held steady in 2025, with the 10 largest auditors handling 65% of audits, and the rest going to smaller firms, according to Ideagen Audit Analytics' annual "
Deloitte held onto the top spot, which it took up in 2024, with 926 SEC registrant clients in 2025, and 15% of the market. Ernst & Young dropped a percentage point but held onto second place, with 799 clients and 13%, while PwC held steady in third with 744 clients and 12% of the market, and KPMG grew its share to 11%, with 639 clients.
Two firms joined the Top 10 public company audits, both thanks to major mergers: CBIZ CPAs, which combined with Marcum in 2024, and Baker Tilly, which merged with Moss Adams in 2025.
Beyond the Top 10, a total of 219 other firms handle the remaining 35% of SEC registrant audits -- a breakdown that stayed the same.
All of these market shares exclude the market for special purpose acquisition company audits, which are overwhelmingly handled by mid-tier and smaller firms, and only made up 4% of the overall market in 2025 in any case.
That 4%, however, represents a jump from 2024, when SPACs were 2.4% of the market. There were 236 SPAC registrants last year, against 6,050 non-SPAC registrants. That's 86 more SPACs than in 2024, but 235 fewer traditional public companies, down from 6,285.
The Ideagen Audit Analytics report covers a number of other aspects of the audit market, including auditor breakdowns by:
- Filer status, including non-accelerated filers (52%), accelerated filers (12%) and large accelerated filers (33%);
- Exchange (NASDAQ, the New York Stock Exchange, and over the counter);
- Jurisdiction (U.S. and foreign);
- Region of the U.S.; and,
- Industry.
The report is
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