The big 4 accounting firms are Deloitte, PwC, EY and KPMG, the four largest professional services networks in the world. They audit most large public companies and earned more than $220 billion combined in FY2025. This guide covers what they do, how they compare, what working there is like, and the latest news.
What Are the Big 4 Accounting Firms?
The Big 4 are Deloitte, PricewaterhouseCoopers (PwC), Ernst & Young (EY) and KPMG. Together they dominate audit, tax and advisory work, especially for publicly traded companies.
Three of them have headquarters in London: Deloitte, PwC and EY. KPMG is based in Amstelveen, in the Netherlands. People also call them the Big Four, the major accounting firms, or global accounting networks.
Each one is a network of member firms, not a single company. That matters when you read the news. A scandal at one country’s office does not always reflect the rest of the network.
Big 4 Firms Ranked by Revenue (2025–2026)
Deloitte is the largest of the Big 4, with $70.5 billion in revenue in FY2025. PwC is second, followed by EY and KPMG.
| Firm | HQ | FY2025 Revenue | Employees | Known Strengths |
| Deloitte | London, UK | $70.5B | ~470,000 | Consulting, audit |
| PwC | London, UK | $56.9B | ~364,000 | Audit, tax |
| EY | London, UK | $53.2B | ~393,000 | Tax, assurance |
| KPMG | Amstelveen, NL | $39.8B | ~276,000 | Audit, risk advisory |
Growth continued despite the scandals. Deloitte grew 4.9% in US dollars, and KPMG grew 5.1% in local currency.
Services Offered by Big 4 Firms
Big 4 firms sell audit, tax, consulting and advisory services. Audit is where they built their name, but consulting and advisory now drive much of the growth.
Core services include:
- Audit and assurance: financial statement audits and internal controls
- Tax advisory: compliance, planning, international tax and dispute resolution
- Management consulting: strategy, digital transformation and organizational change
- Financial advisory: mergers and acquisitions, valuation, restructuring and forensic accounting
- Risk advisory: cybersecurity, regulatory compliance, internal audit and ESG reporting
- Other services: actuarial work, corporate finance and legal services in select countries
Many firms are also moving into managed services. These are multi-year contracts where the firm runs parts of a client’s back office. Bloomberg Tax reports that these fees now drive significant revenue at all four firms.
History: From Big Eight to Big Four
The Big 4 exist because the industry shrank from eight major firms to four through mergers and one major collapse. The “Big Eight” merged down to the “Big Five” over the 1980s and 1990s.
The key dates:
- 1845: Deloitte founded in London
- 1987: KPMG formed through a merger
- 1989: EY formed (Ernst & Whinney and Arthur Young)
- 1998: PwC formed (Price Waterhouse and Coopers & Lybrand)
- 2001–2002: The Enron scandal breaks and Arthur Andersen collapses
Arthur Andersen was founded in Chicago in 1913. After it fell, four firms were left at the top. That concentration still worries regulators today.
Big 4 vs Mid-Tier Accounting Firms
Choose a Big 4 firm for global reach and brand power. Choose a mid-tier firm for balance, speed and hands-on work. Mid-tier firms include BDO, Grant Thornton and RSM.
| Factor | Big 4 | Mid-Tier |
| Revenue per firm | 40B–70B | 5B–15B |
| Typical clients | Fortune 500, multinationals | Mid-market, private companies |
| Prestige | Highest | Moderate |
| Work-life balance | Demanding in busy season | Generally better |
| Promotion speed | Slower | Faster |
| Exit options | Top-tier (PE, banking, corporate) | Strong (regional, industry) |
For businesses, the rule is simple. A public company needing global audit coverage or complex M&A and tax advice usually needs the Big 4. A private or small company often gets more partner attention, and lower fees, from a mid-tier firm.
Careers at Big 4 Firms: Salaries, Internships and Hiring
Getting hired at a Big 4 firm is competitive, but it is very doable with early preparation. Most firms want a minimum 3.0 GPA, and strong applicants often have 3.3 or higher.
GPA is not everything. A 3.4 with leadership roles and Excel or data skills can beat a 3.8 with no activities.
On pay, the research shows starting salaries differ by only about 5–10% between Big 4 and mid-tier firms. Because the gap is small, culture and growth should matter more than salary alone.
Here is a simple path to an internship:
- Keep your GPA at 3.0 or higher, and aim for 3.3+.
- Take accounting, finance and business analytics courses.
- Join accounting clubs and case competitions.
- Meet recruiters at career fairs, on LinkedIn and through alumni.
- Apply early. Many applications open 6–9 months before the start date.
- Prepare for online assessments and behavioral interviews.
- Send a thank-you email within 24 hours of each interview.
Common interview questions include “Why do you want to work at this firm?” and “Tell me about a time you worked in a team under pressure.” Use the STAR method (situation, task, action, result) to answer them. If you miss the summer deadline, try off-cycle internships. They tend to be less competitive.
Big 4 Work-Life Balance: What to Expect
Work-life balance at the Big 4 depends on your service line, and busy season is tough. Audit and tax teams often work 60–80 hour weeks from January to April.
Consulting roles are project-based. The hours spike during deadlines, and travel is common. Mid-tier firms are generally easier on hours.
Don’t rely on one source. Check Vault rankings, read Glassdoor reviews for your office and service line, and ask recruiters what hours look like in practice. Talking to current employees helps most.
How Big 4 Firms Use AI and Technology
All four firms now use AI agents at scale, and they are investing billions. The goal is to automate repetitive work so people can focus on advice.
- EY: 150 AI agents serve 80,000 tax professionals and have handled 3 million+ compliance cases. EY and Microsoft also announced a $1 billion AI investment for client work.
- KPMG: Committed $2 billion over five years, targeting $12 billion in AI-enabled revenue.
- Deloitte: Built Zora AI with Nvidia for invoice processing.
- PwC: Uses GL.ai and AI tax agents for journal entry review and audit work.
For job seekers, this does not mean fewer jobs overnight. Firms don’t publish headcount effects, but entry-level work is shifting toward data analysis, AI oversight and client communication. Build “T-shaped” skills: deep accounting knowledge plus data analytics and AI literacy.
Recent Big 4 Scandals and Regulatory Scrutiny
The most serious recent scandals hit the Australian offices of PwC, EY and KPMG. Regulators are now paying close attention.
- 2023, PwC Australia: Leaked confidential tax policy to help clients avoid new laws. PwC lost government contracts and sold its advisory business for A$1.
- 2025, EY Australia: Two employees accessed the prime minister’s personal banking details and were sacked.
- 2026, KPMG Australia: Shared confidential client information to win audit bids and mishandled a whistleblower complaint. The CEO resigned, about 400 jobs were cut (27 partners and 360 staff), and government contracts were lost.
The financial hit is visible. New Big 4 federal contracts in Australia fell to A348millionin2025,downfromA637 million in 2024. ASIC is reviewing 551 audit misconduct complaints across Big 4 firms in Australia. In July 2026, Australia announced plans to increase oversight, and proposals include limits on partner numbers and separating audit from consulting. KPMG also named Gary Wingrove as its new global chairman and CEO.
Remember that these are regional problems. Check the reputation of the specific office, not just the global brand.
PCAOB Audit Quality: Are Big 4 Audits Reliable?
Big 4 audit quality is improving, at least by the regulator’s own numbers. The PCAOB’s combined Part I.A deficiency rate fell from 26% in 2023 to 20% in 2024 and 8% in 2025.
| Firm | 2025 Deficiency Rate |
| Deloitte | 5% |
| EY | 5% |
| PwC | 9% |
| KPMG | 13% |
Lower is better. Some commentators have asked whether the results are “too good to be true,” so treat one year of data with care. Still, the trend is clearly positive.
How to Get Hired at a Big 4 Firm
To get hired, start early, build a balanced profile and network before you apply. Start preparing in your sophomore year for summer internships.
Avoid these common mistakes:
- Assuming all four firms are the same
- Applying too late
- Focusing only on GPA
- Skipping behavioral interview practice
- Applying cold without networking
- Accepting the first offer without comparing others
Research each firm’s personality too. Deloitte stresses innovation and consulting, PwC talks about building trust, EY highlights entrepreneurial spirit, and KPMG focuses on integrity and audit quality. Ask smart questions in interviews, such as “How has AI changed your team’s workflow?”
Future of Big 4 Accounting Firms: Trends and Challenges
The future of the Big 4 will be shaped by AI, regulation and competition from mid-tier firms. Revenue is still growing, but trust has taken a hit.
Watch these trends:
- AI-driven automation and managed services contracts
- Possible audit and consulting separation
- Rising demand for ESG reporting and cybersecurity advice
- Stricter oversight from the PCAOB and ASIC
The firms that rebuild trust while adopting technology fastest will likely lead the next decade.
Conclusion
The big 4 accounting firms remain the top choice for global audits and elite careers. They also face real pressure from scandals, regulators and AI. Match the firm to your goals, check the specific office’s reputation, and compare it with mid-tier options before you decide.
FAQs
What are the Big 4 accounting firms?
Deloitte, PwC, EY and KPMG. They are the four largest professional services networks in the world by revenue.
Which Big 4 firm is the largest?
Deloitte, with 70.5billioninFY2025revenue.PwC(56.9B), EY (53.2B)andKPMG(39.8B) follow.
What services do Big 4 firms offer?
Audit and assurance, tax, management consulting, financial advisory and risk advisory. Some also offer legal, actuarial and ESG services.
How did the Big 4 become the Big 4?
Mergers cut the Big Eight to the Big Five. Arthur Andersen collapsed in 2002 after the Enron scandal, leaving four.
Are Big 4 internships worth it?
For most students, yes. They offer brand value, training and strong exit options, though hours can be long.
What is Big 4 work-life balance like?
It depends on the service line. Audit and tax can mean 60–80 hour weeks from January to April.
Should I choose Big 4 or mid-tier?
Choose Big 4 for prestige and exit options. Choose mid-tier for better balance and faster promotion.
How are Big 4 firms using AI?
EY runs 150 AI agents for 80,000 tax professionals. KPMG committed $2 billion over five years. Deloitte uses Zora AI and PwC uses GL.ai.
What are recent Big 4 scandals?
PwC Australia’s 2023 tax leak, EY Australia’s 2025 banking data breach, and KPMG Australia’s 2026 audit-leak scandal.
Are Big 4 audits reliable?
Results are improving. The combined PCAOB deficiency rate fell from 26% in 2023 to 8% in 2025.