By 2025, the world's largest professional services firms—PwC, Deloitte, EY, and KPMG—launched multi-agent AI platforms. These platforms, collectively known as the Big 4 AI agents, are more than just tools.
The Big 4 are the four largest global professional services networks that dominate audit and assurance, tax, and advisory work for companies and governments worldwide. They are Deloitte, PwC, EY, and KPMG.
The Big 4 are the largest accounting and auditing firms in the world: Deloitte LLP (Deloitte), PricewaterhouseCoopers (PwC), Ernst & Young (EY) and Klynveld Peat Marwick Goerdeler (KPMG). They're so big that their joint revenue in 2024 was—you guessed it—$212 billion. Let's go into more detail.
The Big Eight consisted of Arthur Andersen, Arthur Young, Coopers & Lybrand, Deloitte Haskins and Sells, Ernst & Whinney, Peat Marwick Mitchell, Price Waterhouse, and Touche Ross.
KPMG is probably the lowest tier and I would say they start you off with a lower base than other firms. The ranking among the other three is usually Deloitte, PwC and EY, though in financial services, EY is probably 2nd. Deloitte has the strongest digital practice and it's strongest in digital transformation.
Walt Disney company and PWC. We begin with Disney, in 2023 one hundred years old. At $180 billion, it is the largest entertainment corporation in the world and its auditor, Price Waterhouse Coopers (PwC) is one of the Big 4 global accountant partnerships.
AI juggernaut Nvidia, is being audited by PwC for its 2026 fiscal year, ending January 31, 2026, according to the Nvidia Corporation Annual Review. PwC has audited Nvidia since 2004, the report notes.
The Big 4 accounting firms salary ranges from $55,000 for associates to $390,000+ for directors, with partners earning $250,000 to $5 million. Consulting roles pay the most, while audit and tax salaries start lower, showing function is more important than the firm.
The top 10 largest accounting firms by revenue:
4️⃣ 𝐊𝐥𝐲𝐧𝐯𝐞𝐥𝐝 𝐏𝐞𝐚𝐭 𝐌𝐚𝐫𝐰𝐢𝐜𝐤 𝐆𝐨𝐞𝐫𝐝𝐞𝐥𝐞𝐫 (𝐊𝐏𝐌𝐆) Among the Big 4, KPMG is the oldest firm, with its earliest parent company founded in 1818. In 1911, William Barclay Peat & co merged with Marwick Mitchell & Co to form Peat Marwick.
History of the Big 4 accounting firms
In the late 1990s, the Big 6 became the Big 5 when Price Waterhouse merged with Coopers and Lybrand to form PricewaterhouseCoopers (later stylised as PwC). Five became four in 2001 after the insolvency of Arthur Andersen due to the firm's involvement in the Enron scandal.
The single most important certification needed for a Big 4 career is a Certified Public Accountant (CPA) license.