Auditor changes roundup: 2025 annual summary
The benefits of firm mergers continued to deliver in 2025. CBIZ CPAs PC was the big winner in terms of net client gains with 154 net gains in 2025. The firm only experienced 14 departures while engaging 168 SEC registered companies, of which 152 were former Marcum clients. Baker Tilly US LLP followed in second place with 66 net client gains, experiencing only five departures, benefiting from their merger: with 63 of the engagements former Moss Adams clients. KPMG, the only member of the Big Four to make it into the top five firms in net client gains, had a total of 42 gains but also experienced 22 departures for twenty net gains. LAO Professionals is a new addition, both to auditing SEC clients and to our top five. They were engaged by 18 former clients of the previously PCAOB registered firm, Olayinka, Oyebola & Co., also located in Nigeria.
Global and national firms
The ten largest audit firms experienced both highs and lows in terms of engagements and departures in 2025.
Deloitte saw 42 new engagements, matching KPMG for the most client gains among the Big Four. Deloitte also experienced 28 departures for a net gain of 14 clients. PricewaterhouseCoopers gained 18 new clients but experienced 16 departures for a net gain of only two clients. BDO USA LLP gained 21 clients but lost 14, resulting in a net gain of seven clients.
EY faced the most significant challenges among the Big Four with 49 departures and only 13 engagements during the year for a net loss of 36 clients. 37 of EY's departures were to other Big Four competitors.
Major mergers
Audit firm mergers continued to be a catalyst for significant client movement. The largest merger of the year occurred between Baker Tilly and Moss Adams in a $7 billion transaction that completed in June 2025, creating the sixth largest advisory CPA firm in the United States. Baker Tilly gained 71 new engagements in 2025 with only five departures, resulting in 66 net client gains.
CBIZ CPAs PC continued to benefit from its November 2024 acquisition of Marcum's attest business. CBIZ gained 168 new engagements with only 14 departures in 2025, far exceeding all other firms in net client gains.
Forvis Mazars, who merged in 2024, had a net engagement loss of ten audit clients.
Marcum Asia added 11 new audit engagements and combined with the former Marcum business loss of 207, ended with net engagement losses of 196.
Market cap and audit fee gains
Amounts shown in billions USD
KPMG ranked highest in terms of net client market cap gained. Their 42 engagements and 22 departures led to a net client market cap gain of $135.6 billion. KPMG also led all auditors in net audit fees gained with $78.1 million.
PricewaterhouseCoopers gained clients with a net market cap of $74.1 billion, ranking second, while Deloitte followed with $64.3 billion in net market cap gains. Despite having fewer net client gains overall, these Big Four firm clients commanded significantly higher market capitalization than their competitors.
Baker Tilly US LLP gained clients with a net market cap of $22.6 billion, while CBIZ CPAs PC, despite having the most net client gains, gained clients with a net market cap of $22.0 billion. Baker Tilly's $53.3 million in net audit fees gained ranked third among all auditors, while CBIZ's $67.1 million ranked second behind only KPMG.
BDO USA LLP gained $38.3 million in net audit fees, ranking fourth, despite experiencing a net loss of $4.0 billion in client market cap. Deloitte rounded out the top five with $19.0 million in net audit fees gained.
Filer Status
Deloitte led large accelerated filer status for a net gain of 14 clients. KPMG followed with seven, CBIZ CPAs PC with five, then Baker Tilly US LLP and PricewaterhouseCoopers both at four.
For accelerated filers, Baker Tilly led with 19 new engagements and one departure. KPMG followed in second with 11 net gains, while CBIZ CPAs PC gained eight net accelerated filer clients.
CBIZ CPAs PC dominated in engagements for non-accelerated filers a with 150 gains and 11 losses for 139 net gains. Baker Tilly followed with 43 gains and three losses for 40 net gains. HTL International LLC and Enrome LLP tied for third place with 14 net gains each. HTL International gained 16 clients and lost two, adding $5.0 million in net audit fees and $1.8 billion in net market cap. Enrome gained 18 clients overall with three departures for 15 net gains, adding $5.4 million in net audit fees and $2.2 billion in net market cap. Assentsure PAC rounded out the top five with 12 net gains, gaining $3.8 million in net audit fees.
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Marie is a CPA and Accounting Research Manager at Ideagen, where she leads the research team and serves as a subject matter expert for Audit Analytics. With thirty years of experience spanning public accounting and corporate finance, Marie began her career at PwC managing audits of SEC registrants and international entities. She later specialized in post-acquisition integration, leading accounting teams, ERP implementations, and financial reporting and analysis. Her diverse leadership experience across accounting, IT, risk management and HR gives her a comprehensive perspective on financial operations and compliance.
