Who Are the Big 4 Accounting Firms?
- Greg Pacioli
- Aug 1, 2025
- 3 min read
Updated: Aug 3, 2025
The "Big 4" refers to the four largest global accounting and professional services firms that really lead the pack. These companies have a huge presence in the industry, providing a variety of services such as auditing, tax assistance, consulting, risk management, and financial advice to some of the biggest institutions around the globe. With hundreds of thousands of employees working for them, they operate on a worldwide scale and together pull in over $200 billion in annual revenue.
Why Are They Called the Big 4?
Have you ever wondered why we refer to them as the Big 4? Well, it all goes back to the history of the accounting industry. Over the years, there were several mergers that whittled down the number of major firms from the "Big 8" to the "Big 5." Then, after the fall of Arthur Andersen in 2002, we ended up with what we now know as the "Big 4."
The Big 4 Accounting Firms (Ranked by Revenue)
Based on the global revenue data for from last year, here’s how the Big 4 stack up from the largest to the smallest:
1. Deloitte
Revenue: $65+ billion
Headquarters: New York, USA
Employees: 456,000+
Specialties: Deloitte is the largest of the Big 4, both in terms of revenue and workforce. It's widely recognized for its robust consulting and advisory services, especially in areas like technology, strategy, and digital transformation. The firm has carved out a reputation as a frontrunner in cybersecurity, cloud solutions, and analytics consulting, with its consulting division often outpacing its audit services in terms of growth.
Revenue: $54+ billion
Headquarters: London, UK
Employees: 364,000+
Specialties: PwC has a solid foothold in both audit and tax services, but it really shines when it comes to navigating complex international tax structures, providing assurance services, and offering deal advisory. The firm also puts a lot of effort into ESG (Environmental, Social, and Governance) advisory services.
Revenue: $50+ billion
Headquarters: London, UK
Employees: 395,000+
Specialties: EY is highly regarded for its support of entrepreneurs, particularly through its Entrepreneur of the Year program. The firm has also built a solid reputation in Transaction Advisory Services (TAS), especially when it comes to mergers and acquisitions.
4. KPMG
Revenue: $37+ billion
Headquarters: Amstelveen, Netherlands
Employees: 275,000+
Specialties: KPMG may be the smallest among the Big 4, but it really shines in audit and assurance, especially within the financial services sector. They also have a strong presence in areas like risk advisory, forensic accounting, and regulatory compliance, often catering to major banking and insurance clients.
Big 4 Accounting Ranking Table
Firm | Revenue | Employees | Countries | Offices |
|---|---|---|---|---|
Deloitte | $64.9B | 456,000+ | 150+ | 700+ |
PwC | $53.1B | 364,000+ | 151 | 742 |
EY | $49.4B | 395,000+ | 150+ | 700+ |
KPMG | $36.4B | 275,000+ | 143 | 650+ |
🏅 Runner‑Ups: Ranks 5 & 6
After the Big 4, there's a significant revenue drop but these firms remain major players.
5. BDO Global
Global Revenue: ~$14 billion
Employees: ~120,000
Countries: 150+
Offices: ~1,200
Specialties: BDO is the fifth-largest accounting network, with a strong focus on middle-market clients. It specializes in audit, tax, consulting, and business advisory. It's recognized for delivering personalized client service while maintaining a broad global footprint.
6. Baker Tilly + Moss Adams (Combined)
Combined U.S. Revenue: > $3 billion
Employees: ~11,500
Formed by Merger: Baker Tilly (U.S.) and Moss Adams merged in 2025 to become the sixth-largest U.S. CPA advisory firm.
Specialties: They focus on the mid-market and have a broad geographic reach across the East, Central, and West U.S. Together, these firms offer strong advisory, tax, and assurance services, all supported by private equity backing.
Final Thoughts on the Big 4
While the Big 4 accounting firms certainly hold a strong grip on the global market thanks to their vast resources, scale, and well-known brands, that level of service often comes with a steep price.
For large multinational corporations, Fortune 500 companies, or those facing intricate audits, investing in the Big 4 might be justified.
However, if you're a real estate investor (particularly one interested in cost segregation) you might find that a specialized boutique firm is a better fit.
Many mid-sized firms and niche providers bring a wealth of knowledge in real estate depreciation, IRS compliance, and tax strategy, often at a much lower cost.
When it comes to fine-tuning your tax strategy, particularly in areas like cost segregation, find a firm that aligns with your specific needs.
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