The Big 4 Accounting Firms: Complete Guide to Deloitte, PwC, EY, and KPMG

The Big 4 accounting firms are Deloitte, PwC (PricewaterhouseCoopers), EY (Ernst and Young), and KPMG. Together, the four big accounting firms audit the majority of the world’s largest publicly traded companies, provide tax advisory, consulting, and financial advisory services to organizations across every industry, and employ over one million professionals globally.

Understanding what each firm does, what it is known for, how large it is, and how the Big 4 differ from each other helps businesses, finance professionals, and job seekers make better decisions about which firm they engage or pursue.

This guide covers what the Big 4 accounting firms are, profiles each of the four big accounting firms in detail, compares them across key dimensions, and explains what working with or for the Big 4 means in practice.

Key Takeaways

In this blog, you’ll learn:

• Who are the Big 4 accounting firms, what they do, and why they dominate global professional services.
• What Deloitte, PwC, EY, and KPMG are each known for, including their size, revenue, and primary service strengths.
• How the four big accounting firms compare across audit, tax, advisory, and consulting services.
• What it is like to work at a Big 4 accounting firm and what career opportunities each firm offers.
• When a business should engage the Big 4, when a regional or specialized firm is the better choice, and what to consider in that decision.

The Big 4 Accounting Firms

Big 4 Accounting Firms: Key Industry Data

What Are the Big 4 Accounting Firms?

The Big 4 accounting firms are the four largest professional services firms in the world by revenue: Deloitte, PwC (PricewaterhouseCoopers), EY (Ernst and Young), and KPMG.

Accounting Big 4 refers to the four firms that dominate global professional services. What are the Big 4 accounting firms in terms of what they actually do? Each of the four big accounting firms provides audit and assurance, tax advisory, management consulting, financial advisory, and risk services to corporations, governments, nonprofits, and financial institutions worldwide.

The Big 4 are not a single organization. Each firm is a global network of independent member firms, legally separate in each country they operate in, united under a common brand, methodology, and quality standards. The Big 4 companies collectively audit the vast majority of Fortune 500 and FTSE 100 companies.

According to Public Company Audit Analytics, the Big 4 accounting firms audit over 99% of Fortune 500 companies. Their dominance in large-company audit work is the result of regulatory requirements, liability considerations, and the global infrastructure required to audit multinational corporations across dozens of jurisdictions simultaneously.

Why Are They Called the Big 4?

The term ‘Big 4’ reflects the consolidation of the global accounting industry that occurred primarily in the 1990s and early 2000s. The industry was once the ‘Big Eight,’ then the ‘Big Six,’ then the ‘Big Five,’ before the collapse of Arthur Andersen in 2002 following the Enron accounting scandal reduced the group to four.

Each consolidation resulted from mergers between major firms. The current 4 big accounting firms absorbed dozens of predecessor practices over decades:

• Deloitte absorbed Touche Ross, Coopers (in some regions), and dozens of national practices.
• PricewaterhouseCoopers was formed in 1998 from the merger of Price Waterhouse and Coopers & Lybrand.
• Ernst and Young was formed from Ernst & Whinney and Arthur Young merging in 1989.
• KPMG (Klynveld Peat Marwick Goerdeler) was formed in 1987 from the merger of Peat Marwick International and KMG Group.

What Is Deloitte? Overview, Services, and What It Is Known For

Deloitte is the world’s largest professional services firm by revenue, generating $70.5 billion in FY2025. Founded in 1845 by William Welch Deloitte in London, the firm has grown into a global network operating in over 150 countries with more than 470,000 professionals.

What is Deloitte known for? Deloitte is particularly recognized for its strength in consulting and technology services, which account for a larger share of its total revenue than at any other Big 4 firm. Deloitte Consulting is one of the world’s largest management consulting practices, competing directly with McKinsey, Bain, and BCG in the strategy and technology transformation space.

Deloitte’s full legal name is Deloitte Touche Tohmatsu Limited (DTTL), headquartered in London, with member firms operating as legally separate entities in each jurisdiction.

Deloitte: Core Services and Strengths

Deloitte’s University, a leadership development campus in Westlake, Texas, is one of the most recognized symbols of the firm’s investment in talent development. The firm consistently ranks among the top employers for finance and consulting graduates globally.

What Is PwC (PricewaterhouseCoopers)? Overview, Services, and What It Is Known For

PwC, short for PricewaterhouseCoopers, is the second-largest Big 4 accounting firm by revenue, generating $56.9 billion in FY2025. PwC operates in over 152 countries with more than 364,000 employees and is widely regarded as the gold standard for audit quality and assurance services.

What is PwC known for? PwC is best known for its audit and assurance practice, which is considered by many institutional investors and regulators to be the most rigorous and thorough among the Big 4 accounting firms. PwC audits a larger share of the world’s largest financial institutions than any other Big 4 firm.

PricewaterhouseCoopers was formed in 1998 through the merger of Price Waterhouse (founded 1849) and Coopers and Lybrand (founded 1854), both among the original Big Eight accounting firms. Ernst & Young Global Limited uses the EY brand globally today.

PwC: Core Services and Strengths

PwC is also well known for its annual reports and research publications, including the Global CEO Survey (one of the most cited business research studies in the world) and its annual State of Climate Tech report. These publications give PwC significant thought leadership authority across finance, technology, and sustainability.

What Is EY (Ernst and Young)? Overview, Services, and What It Is Known For

EY, formally known as Ernst and Young Global Limited, is the third-largest Big 4 accounting firm by revenue, generating $53.2 billion in FY2025. EY operates across 150 countries with approximately 406,000 professionals and is particularly recognized for its transactions, strategy, and entrepreneurship advisory practices.

What is EY known for? EY is widely regarded as the leading Big 4 firm for transactions advisory and private equity work. EY-Parthenon, the firm’s strategy arm, is one of the most recognized strategy advisory practices globally. EY also runs the EY Entrepreneur of the Year program, one of the most prestigious business recognition programs worldwide, which gives the firm a distinctive positioning in the entrepreneur and growth business space.

Ernst and Young was formed in 1989 through the merger of Ernst and Whinney and Arthur Young. Ernst and Young is headquartered in London, with member firms operating as independent entities in each country. The rebranding to EY occurred in 2013 as part of a global brand refresh.

EY: Core Services and Strengths

EY made global headlines in 2022 when it announced a potential split of its audit and consulting businesses (known internally as Project Everest). The proposed separation was ultimately abandoned in 2023 after partners in the US voted against it, but the episode highlighted the ongoing tension between audit independence requirements and the growth of lucrative consulting services at the Big 4 firms.

What Is KPMG? Overview, Services, and What It Is Known For

KPMG is the fourth-largest of the Big 4 accounting firms by revenue, generating $39.8 billion in FY2025. KPMG stands for Klynveld Peat Marwick Goerdeler, reflecting the four firms whose merger created the global practice in 1987. KPMG operates in 143 countries with over 276,000 professionals.

What is KPMG known for? KPMG is particularly recognized for its strength in audit, tax, and risk advisory, with a historically strong focus on the financial services, government, and public sector industries. KPMG’s audit practice is considered among the most technically rigorous in the profession, with the firm placing a strong emphasis on audit quality and professional standards.

KPMG is headquartered in Amstelveen, Netherlands, making it the only one of the Big 4 accounting firms not headquartered in London. The full name Klynveld Peat Marwick Goerdeler reflects the founding firms: Klynveld Kraayenhof (Netherlands), McLintock Main Lafrentz (later Peat Marwick Mitchell), and Deutsche Treuhandgesellschaft/Goerdeler.

KPMG: Core Services and Strengths

KPMG has faced notable challenges in recent years, including audit quality findings by the PCAOB in the UK and US that resulted in regulatory scrutiny. The firm has invested significantly in audit quality improvement programs as a result. Despite these challenges, KPMG remains a dominant force in global professional services and a highly sought-after employer for accounting graduates.

Big 4 Accounting Firms Compared: Deloitte vs PwC vs EY vs KPMG

All four of the top 4 accounting firms provide the same core services: audit, tax, advisory, and consulting. The differences lie in scale, specialization, industry focus, and cultural identity.

Who are the Big 4 accounting firms best suited for? The answer depends on what a client needs and which firm has the deepest expertise in the relevant industry or service area.

Which Big 4 Firm Is Best for Different Needs?

• For large-scale technology transformation: Deloitte’s consulting arm is the largest among the Big 4 and competes directly with McKinsey and BCG for major transformation engagements.
• For financial services audit and assurance: PwC has the largest market share in financial services audit and is regarded by many regulators and institutional investors as the standard-setter for financial institution audits.
• For M&A transactions and private equity: EY is widely recognized as the leading Big 4 firm for transactions advisory work, with EY-Parthenon providing top-tier strategy and due diligence services.
• For government, public sector, and risk advisory: KPMG has historically been the strongest Big 4 firm in government and public sector engagements, with deep expertise in regulatory compliance and risk management.

What Is It Like to Work at a Big 4 Accounting Firm?

The Big 4 accounting firms are among the most sought-after employers for accounting, finance, and business graduates worldwide. A Big 4 career offers structured professional development, global exposure, CPA exam support, and a recognized credential that opens doors across the finance and business world.

Working at a Big 4 firm is demanding. Long hours, particularly during audit busy season (January through April) and around major transaction deadlines, are part of the culture. In return, the learning curve is steep and the professional network built during even a two to four year Big 4 tenure is often career-defining.

According to the AICPA, a Big 4 background is one of the most common pathways into CFO, controller, and senior finance leadership roles at Fortune 500 companies. Many private equity firms, investment banks, and consulting firms specifically recruit professionals with Big 4 audit or advisory experience.

Big 4 Career Structure

Big 4 Salary Ranges (US Market, 2024)

When Should a Business Use the Big 4 vs a Regional or Specialized Accounting Firm?

The Big 4 accounting firms are the right choice for large, complex, and multinational organizations with audit, tax, or advisory needs that require global infrastructure and the deepest available expertise. For smaller and mid-market businesses, the Big 4 are often not the most practical or cost-effective choice.

Big 4 firms charge premium rates that reflect their brand, global reach, and the talent they employ. A mid-market manufacturing company that needs an annual audit and tax preparation does not need the overhead of a Big 4 engagement. A regional CPA firm or a specialized accounting and bookkeeping service provider will often deliver stronger fit, better accessibility, and practical support for mid-market needs.

According to the AICPA, the Next 10 accounting firms (firms ranked 5 through 14 by revenue, including Grant Thornton, RSM, BDO, and Moss Adams) collectively serve the mid-market exceptionally well and are frequently the preferred choice for businesses between $10M and $1B in revenue.

Common Misconceptions About the Big 4 Accounting Firms

Several widely held beliefs about the Big four accounting firms are either incomplete or inaccurate.

• The Big 4 are a single organization: each firm is a global network of legally independent member firms, not one company. Deloitte UK and Deloitte US are separate legal entities sharing a brand, methodology, and quality standards, not a single employer.
• Big 4 experience is only for public accounting: the Big 4 offer far more than audit. Consulting, financial advisory, risk advisory, strategy, and tax services together account for the majority of Big 4 revenue. Many professionals build entire careers in non-audit practices.
• You need to stay at a Big 4 firm to have a top finance career: the typical Big 4 tenure for audit and advisory professionals is two to four years before moving into industry roles as controllers, CFOs, or private equity professionals. The Big 4 are often a prestigious launchpad, not a long-term destination.
• The Big 4 audit opinion guarantees financial accuracy: a clean audit opinion means the auditor found no material misstatements under GAAP. It does not guarantee that the business is well-managed, that all information has been disclosed, or that fraud does not exist at below-material thresholds.
• Mid-market businesses need the Big 4: for most businesses below $500M in revenue that are not publicly traded, the Big 4 are an expensive choice with limited incremental value over a well-qualified regional firm or specialized outsourced accounting provider.

Frequently Asked Questions

What are the Big 4 accounting firms?

The Big 4 accounting firms are Deloitte, PwC (PricewaterhouseCoopers), EY (Ernst and Young), and KPMG.

Together, the four big accounting firms are the world’s largest professional services organizations, providing audit, tax, advisory, and consulting services to corporations, governments, and financial institutions across more than 150 countries. They audit over 99% of Fortune 500 companies.

Who are the Big 4 accounting firms?

The Big 4 accounting firms are Deloitte (the largest by revenue), PwC (PricewaterhouseCoopers), EY (Ernst and Young), and KPMG (Klynveld Peat Marwick Goerdeler).

All four are headquartered in Europe (three in London, KPMG in Amstelveen, Netherlands) but operate as global networks with member firms in over 140 countries. The Big 4 companies collectively employ over 1.4 million professionals worldwide.

What do the Big 4 accounting firms do?

The Big 4 accounting firms provide four core services: audit and assurance, tax advisory, management consulting, and financial advisory.

Audit and assurance is their most regulated function: Big 4 auditors independently verify that financial statements are accurate and GAAP-compliant. Tax advisory covers corporate tax strategy, international tax structuring, transfer pricing, and compliance. Consulting covers technology transformation, operations, and strategy. Financial advisory covers M&A transactions, restructuring, forensic accounting, and valuations.

Where are the Big 4 accounting firms located?

Three of the Big 4 accounting firms are headquartered in London, UK: Deloitte, PwC, and EY. KPMG is headquartered in Amstelveen, Netherlands.

Despite their European headquarters, all four firms operate as global networks with member firms in over 140 countries. The US is the largest single market for each firm, with major offices in New York, Chicago, Los Angeles, Houston, and other major cities. Each country’s member firm is a legally separate entity operating under the shared brand.

What is big 4 accounting firms?

Big 4 accounting firms is the collective term for the four largest professional services and accounting organizations in the world: Deloitte, PwC (PricewaterhouseCoopers), EY (Ernst and Young), and KPMG.

The Big 4 dominate global audit, tax, and advisory markets. They audit over 99% of Fortune 500 companies, employ more than 1.6 million professionals worldwide, and together generate over $220 billion in combined annual revenue. The term ‘Big 4’ replaced ‘Big 5’ after Arthur Andersen collapsed in 2002 following the Enron scandal.

What is the Big 4 in accounting?

The Big 4 in accounting refers to Deloitte, PwC, EY, and KPMG, the four firms that collectively dominate the global accounting, audit, and professional services industry.

In accounting specifically, the Big 4 are known for setting the standard for audit quality on large public company engagements. They audit the majority of Fortune 500, FTSE 100, and other major stock exchange-listed companies globally. For finance professionals, Big 4 experience is one of the most recognized credentials for senior accounting and CFO roles.

What is Deloitte and what is it known for?

Deloitte is the world’s largest professional services firm by revenue ($70.5B in FY2025) and is known for its consulting and technology transformation practice, which is the largest among the Big 4 accounting firms.

Deloitte’s full name is Deloitte Touche Tohmatsu Limited (DTTL). What is Deloitte known for beyond consulting? Its global audit practice covers major multinational corporations, and its financial advisory team is one of the top M&A and restructuring practices worldwide.

What is PwC (PricewaterhouseCoopers) and what is it known for?

PwC (PricewaterhouseCoopers) is the second-largest Big 4 accounting firm ($56.9B in FY2025) and is known for its audit and assurance practice, particularly in financial services.

PricewaterhouseCoopers was formed in 1998 from the merger of Price Waterhouse and Coopers and Lybrand. What is PwC known for in the market? PwC consistently leads in financial institution audit market share and produces highly cited global research including the annual Global CEO Survey.

What is EY (Ernst and Young) and what is it known for?

EY (Ernst and Young) is the third-largest Big 4 firm ($53.2B in FY2025) and is known for its transactions advisory, private equity work, and strategy practice through EY-Parthenon.

Ernst and Young was formed in 1989 and rebranded as EY in 2013. What is EY known for in professional services? EY is the preferred Big 4 firm for many private equity sponsors and M&A transactions, and the EY Entrepreneur of the Year program is one of the most recognized business award programs globally.

What is KPMG and what does it stand for?

KPMG is the fourth-largest Big 4 accounting firm ($39.8B in FY2025). KPMG stands for Klynveld Peat Marwick Goerdeler, reflecting the founding firms that merged to create it in 1987.

What is KPMG known for? KPMG is recognized for its audit practice, tax advisory, and risk consulting, with particular strength in financial services, government, and public sector engagements. It is the only Big 4 firm headquartered outside London, based in Amstelveen, Netherlands.

What is the difference between the Big 4 accounting firms?

All four big accounting firms provide audit, tax, advisory, and consulting services. The primary differences are in size, revenue, industry specialization, and service line strength.

Deloitte is the largest and strongest in consulting. PwC leads in financial services audit. EY leads in transactions and private equity advisory. KPMG is strongest in government and public sector. For most engagements, the choice between the four big accounting firms comes down to industry expertise, existing relationships, and pricing.

How do the Big 4 compare to mid-market accounting firms?

The Big 4 accounting firms serve primarily large, complex, and multinational organizations. Mid-market firms such as Grant Thornton, RSM, and BDO serve businesses in the $10M to $1B revenue range with comparable technical expertise at lower cost.

For businesses that are not publicly traded and do not require the global infrastructure of a Big 4 firm, a well-qualified regional CPA firm or accounting professional provider typically delivers equal or better value. Big 4 premium pricing is justified primarily by regulatory requirements, global reach, and brand recognition in investor-facing situations.

What are the top 4 accounting firms’ combined revenues?

The top 4 accounting firms generated combined revenues of over $220 billion in FY2025: Deloitte ($70.5B), PwC ($56.9B), EY ($53.2B), and KPMG ($39.8B).

Deloitte has been the largest of the Big 4 by revenue for several consecutive years, driven by the significant scale of its consulting and advisory practices relative to the other firms.

Final Thoughts

The Big 4 accounting firms are not simply large accounting practices. They are global professional services organizations that shape how the world’s largest companies report their finances, manage risk, plan acquisitions, and transform their operations.

For finance professionals, understanding the Big 4 is foundational knowledge. For businesses, knowing what each firm is known for, where its strengths lie, and when it is the right choice versus a more specialized provider leads to better engagement decisions and better outcomes.

At Expertise Accelerated, we work alongside Big 4 firms, regional CPA firms, and internal finance teams to provide accounting and bookkeeping, financial reporting, and CFO advisory services to small and mid-market businesses that need professional-grade financial support without the overhead of a Big 4 engagement.

Schedule a free consultation with Expertise Accelerated to discuss your accounting and financial management needs and find out which level of professional accounting support is the right fit for your business.