Big Four lose share of SEC audits

The top accounting firms lost a piece of market share for public company audits in 2024.

The 10 firms with the most Securities and Exchange Commission audit clients accounted for 65% of the total market (excluding special-purpose acquisition companies), down from 70% in 2023, according to Ideagen Audit Analytics' annual "Who Audits Public Companies" report.

Deloitte overtook Ernst & Young for the top spot, auditing 901 clients compared to EY's 869 clients. EY, which had 971 clients the previous year, dropped over 100 clients as the company sought to tailor its clientele, according to the report. Meanwhile, PricewaterhouseCoopers and KPMG both gained clients and expanded their market share, and Crowe crept back into the top 10 after BF Borgers shut down in May 2023.

There were 6,285 SEC registrants in 2024, down roughly 300 from the previous year and down approximately 600 from 2022. The number of SPACs also dropped to 150, compared to 300 SPACs the prior year. This trend is unsurprising as SPACs that went public during the boom of 2021 have mostly completed their lifecycles.

By jurisdiction, mid-tier firms (defined as the 10 firms with the highest audit fees, excluding the Big Four) lost two points of their U.S. market share, with 18% of market share in 2024 versus 20% in 2023. However, mid-tier firms ate up 26% of foreign market share, up 14 points from the previous year.

Market shares by U.S. region remained largely unchanged year-to-year, with the Big Four holding the largest share of New England (68%) and holding their smallest share in the Southeast (47%). 

By industry, the Big Four lost considerable market share in energy and transportation, from 71% in 2023 to 58% in 2024; their share was eaten up by other firms.

Ideagen's report includes any registrants that filed a periodic report with the SEC after Jan. 1, 2024. The auditor market share figures were as of Jan. 31, 2025.