The Big Four Audit Companies: Who They Are, What They Do and When You Need One

The big four audit companies are Deloitte, PricewaterhouseCoopers (PwC), Ernst & Young (EY) and KPMG. Together, these four professional services networks audit most of the world's largest listed groups and set the reference standard for audit quality. You have heard the name and want facts: who they are, what they do, and whether your business needs one.

This guide answers those questions in order, plus the French angle encyclopaedia entries skip: how the Big Four operate in France, which French rules trigger a statutory audit, and what the alternatives look like. The short version: a few companies need a Big Four. Most need their standard of rigour, delivered by a firm sized to the client.

Who Are the Big Four Audit Companies?

The Big Four are the four largest international networks of professional services firms: Deloitte, PwC, EY and KPMG. They are also called the big four accounting firms, or simply the Big 4. Each one is a network, not a single company. Independent member firms operate under the same brand, methodology and quality controls, so Deloitte SAS, PwC France, EY France and KPMG France are separate French legal entities within their global networks.

All four deliver audit and assurance, tax advisory and consulting to large corporations, banks, governments and institutions. Their combined weight in the audit of major listed companies is what the expression "big four audit companies" describes.

Deloitte

Deloitte is the largest of the four by revenue. For FY2024, the network reported approximately USD 76.9 billion in global revenue and about 460,000 people in over 150 countries. Its consulting arm is the most developed of the four, giving Deloitte a strong position in technology and transformation work alongside audit.

PwC (PricewaterhouseCoopers)

PwC reported approximately USD 55.4 billion for FY2024, with around 370,000 employees. Second-largest of the four, it is especially known for its tax advisory practice, coordinated from London by PwC International Limited.

EY (Ernst & Young)

EY reported approximately USD 51.2 billion for FY2024, with roughly 400,000 employees. Assurance is its core business. EY also attempted, then abandoned, a full separation of its audit and consulting arms under the plan codenamed Project Everest, called off in April 2023.

KPMG

KPMG is the smallest, at approximately USD 38.4 billion for FY2024 and over 270,000 employees. It remains a major player in listed-company audit, coordinated from Amstelveen in the Netherlands.

The Big Four at a glance

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Firm	FY2024 global revenue	Workforce	Founded	Headquarters	Known for
Deloitte	~USD 76.9bn	~460,000	1845	London, UK	Scale, consulting
PwC	~USD 55.4bn	~370,000	1998 (merger)	London, UK	Tax advisory
EY	~USD 51.2bn	~400,000	1989 (merger)	London, UK	Assurance
KPMG	~USD 38.4bn	~270,000	1987 (merger)	Amstelveen, NL	Audit market share

Revenue and headcount are approximate network figures for FY2024, as published in each firm's annual global results and compiled on Wikipedia's Big Four overview. Merger dates mark the creation of today's networks; several of the founding firms date back to the 19th century.

What Services Do the Big Four Offer?

"Audit firms" is the common shorthand, but audit is only one of three service pillars.

Audit and assurance: the regulated core

Statutory audit is the independent verification of a company's annual accounts by an external professional. It is mandatory above legal size thresholds, and it built the Big Four's reputation: they sign off the accounts of listed groups, banks and major institutions. In France the equivalent mission is the commissariat aux comptes, performed by a commissaire aux comptes (statutory auditor). If your company is approaching the French audit thresholds, read our overview of statutory audit services (commissariat aux comptes).

Tax advisory and compliance

The Big Four advise multinational groups on corporate tax structuring, transfer pricing, VAT and cross-border compliance, work that requires deep technical teams and global reach.

Consulting and advisory

Beyond audit and tax, the four firms sell strategy, technology, risk and transformation consulting. This is where the model gets delicate: the network that audits a client can also sell it consulting, a combination regulators treat as a potential conflict of interest.

The distinction to remember: statutory audit is regulated and mandatory above thresholds, consulting is commercial and optional. A firm selling both to the same client faces independence questions, one of the structural criticisms examined below.

Why Are They Called the Big Four?

The label is the product of forty years of consolidation, documented in detail on Wikipedia's Big Four page. The number has only ever gone down.

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From the Big Eight to the Big Four

In the 1980s the top tier counted eight firms: Arthur Andersen, Arthur Young, Coopers & Lybrand, Deloitte Haskins & Sells, Ernst & Whinney, Peat Marwick Mitchell, Price Waterhouse and Touche Ross. Two merger waves cut the list:

• 1989: Deloitte Haskins & Sells combined with Touche Ross to form Deloitte & Touche, while Ernst & Whinney combined with Arthur Young to form Ernst & Young. The Big Eight became the Big Six.

• 1998: Price Waterhouse merged with Coopers & Lybrand to create PwC. The Big Six became the Big Five.

The Arthur Andersen collapse (2002)

The fifth firm, Arthur Andersen, collapsed in 2002. Its audit client Enron had gone bankrupt in late 2001, and Andersen was convicted in June 2002 of obstructing justice over the destruction of audit documents. The Supreme Court later overturned the conviction, but the firm had by then lost its licences and clients. The Big Five became today's Big Four, and the remaining firms shared its audit portfolio.

The scandal also produced the Sarbanes-Oxley Act in 2002, which reshaped audit regulation worldwide: a dedicated US audit regulator (the PCAOB), stricter independence rules, and limits on the consulting an auditor may sell to the companies it audits.

The Big Four's Dominance in the Global Audit Market

Global market share and revenue

For FY2024, the four networks together reported over USD 220 billion in revenue and employ around 1.5 million people. The next tier, global networks such as BDO, Grant Thornton, RSM and Mazars, is international too, but at a fraction of that revenue.

Concentration is sharper still in audit itself: the Big Four audit most S&P 500 companies and more than 90% of the FTSE 350, figures compiled on Wikipedia.

The French audit market: CAC 40 concentration

In France, the Big Four audit nearly all CAC 40 companies, the largest groups listed on Euronext Paris. French public-interest entities must appoint two statutory auditors who sign jointly (the joint audit rule), which keeps the top of the French market slightly wider than its UK or US equivalents.

Below that level, the picture changes completely. A French company must appoint a commissaire aux comptes only when it exceeds, for two consecutive financial years, at least two of three thresholds: total balance sheet above EUR 6 million, turnover excluding VAT above EUR 12 million, and an average permanent workforce above 50 employees (thresholds in force for 2026, raised by the decree of 7 June 2023). Some legal forms and regulated situations follow their own rules, but most SMEs sit below these thresholds and have no statutory audit obligation at all.

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If you run one of those companies, or you are registering a company in France, the practical question is not "which Big Four?" but "which qualified firm, at what level of service?"

Challenges and Criticisms Faced by the Big Four

The criticisms below are structural and industry-level. They are debated by regulators and documented in public market studies, not a judgement about any individual firm or team.

Audit quality and conflicts of interest

Regulator inspections have repeatedly flagged audit quality issues across large firms, including Big Four ones: insufficient challenge of management estimates, gaps in audit evidence. The recurring structural criticism concerns independence: a network that earns consulting revenue from a client it also audits has an incentive to protect that relationship.

Market concentration and lack of choice

With four firms auditing most large listed companies, choice is narrow at the top. UK and EU authorities have both examined whether this concentration raises fees and creates systemic risk: if one of the four failed, as Andersen did in 2002, the market would struggle to absorb its audit portfolio.

Regulatory responses

The main European response is Regulation (EU) No 537/2014, applicable since 2016. It imposes auditor rotation for public-interest entities: a firm may audit the same listed client for 10 years, extendable to 20 after a tender and up to 24 with a joint audit, the option France uses. The same text restricts the non-audit services an auditor may sell to its audit clients.

The Future of the Big Four Audit Firms

Three forces are reshaping the model: technology, sustainability reporting, and the unresolved question of audit and consulting under one roof.

AI and technology in audit

All four networks invest heavily in artificial intelligence and data analytics to automate audit testing and scan complete datasets instead of samples. Done well, this raises audit quality; it also concentrates capability in the firms able to fund the tools.

ESG and sustainability assurance

The EU's Corporate Sustainability Reporting Directive phases in mandatory sustainability reporting, with independent assurance of the published information. The Big Four are positioning themselves to lead this new market as they lead financial audit. For companies in scope, it means new obligations and new fees.

The EY Everest split and its aftermath

EY's attempted separation of its audit and consulting businesses, Project Everest, ran from 2022 and was abandoned in April 2023. Had it succeeded, the other three networks would have faced pressure to follow. Its failure left the core tension untouched: audit and consulting still sit inside the same firms, and regulators still object.

Do You Actually Need a Big Four?

This is the question definitional guides never ask. The Big Four set the global standard for audit methodology, but most businesses in France do not need a firm of 300,000 to 460,000 people to meet it. They need the rigour, in a firm that answers the phone.

When a Big Four makes sense

• Your group is listed, large or multinational, with consolidated accounts across many countries.

• An investor, lender or regulator contractually requires a Big Four signature, as some financing rounds and private equity exits do.

• You need coordinated tax or audit work in dozens of jurisdictions.

In these situations, the scale and methodology of a global network are difficult to replace.

When a human-scale firm is the better fit

• Cost. Big Four fees cover global infrastructure. Below a certain size, you pay for capacity you never use.

• Responsiveness. In a Big Four engagement team, your file is one among many. A smaller firm gives you a named contact available all year, not only at year-end.

• Scope. A firm combining chartered accountancy (expertise comptable) and statutory audit can run your accounts and your legal audit under one roof. That double qualification is uncommon at any size.

• Language. An English-speaking owner in France needs French obligations explained in plain English. That is a capability question, not a size question.

Big Four or human-scale firm: a decision framework

Criterion	Big Four network	Human-scale firm
Company profile	Listed, multinational, heavily regulated	SME, startup, mid-size, founder-led
Statutory audit	Core service at global scale	Available when the firm holds the commissaire aux comptes qualification
Responsiveness	Structured teams, longer turnaround	Direct, year-round contact
Fees	High, driven by scale	Proportionate to company size
Sector depth	Strong on large regulated industries	Strong on SME sectors: real estate, professional practices, services
Working language	Depends on the office and team	Can be French and English as standard

Big Four alternatives in France

The French market has a real mid-tier, led by Mazars, a French-origin network with international reach. Below sit hundreds of registered firms combining expertise comptable and commissariat aux comptes, plus independent boutiques founded by former Big Four professionals.

GME Audit works in this tier. The firm is led by Steeve Elharrar, expert-comptable and commissaire aux comptes, formerly of KPMG and Deloitte, with more than 10 years of combined experience in accountancy, audit and advisory. It covers statutory audit (commissariat aux comptes, apports, fusion, transformation), chartered accountancy and advisory, follows around a hundred files a year, and works in French and English. For growing companies that need management support alongside compliance, it also provides outsourced CFO and controller services.

Request a quote. Tell us your company form, your size and whether you are approaching the audit thresholds. You will get a precise answer, not a template quote. You can also talk to an English-speaking chartered accountant in Paris directly.

FAQ: People Also Ask About the Big Four

Which Big Four firm is the largest?

By FY2024 global revenue, Deloitte is the largest at approximately USD 76.9 billion, ahead of PwC (~USD 55.4 billion), EY (~USD 51.2 billion) and KPMG (~USD 38.4 billion).

Do the Big Four do strategy consulting?

Yes, but differently from the pure strategy firms, McKinsey, BCG and Bain. Big Four consulting grew out of audit and tax, so it leans towards technology, risk, transactions and implementation rather than board-level strategy alone.

How much does a Big Four audit cost?

There is no public fee schedule. Fees depend on the size of the audited entity, its complexity and its sector: a large listed group can pay several million euros a year. For an SME, a Big Four engagement is rarely proportionate, and registered human-scale firms perform the same legal mission at lower fee levels, set by proposal.

Are the Big Four only for accounting?

No. Audit and assurance are the regulated core, but the networks also sell tax advisory, consulting, technology, deal advisory and, increasingly, sustainability assurance. "Accounting firm" undersells them, and obscures a useful fact for smaller companies: statutory audit, the regulated part, is a mission any duly registered firm, including human-scale ones, is qualified to perform.

Conclusion: Big Four Rigour at Human Scale

The Big Four audit companies set the benchmark for audit methodology, and for listed, cross-border groups they are often the right choice. Most businesses in France are not listed cross-border groups: they are SMEs, startups and founder-led companies that need the same standard of work from a firm that knows their file, replies the same week and charges in proportion to their size.

This guide is general information. Which firm fits your situation depends on your legal form, your figures and your audit obligations, and that calls for a case-by-case answer.

Request a quote. Tell us your situation, what you need audited or managed, and where your company stands against the thresholds. We will come back with a precise answer, not a standard form.

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GME Audit is a Paris-based chartered accountancy and statutory audit firm led by Steeve Elharrar, expert-comptable and commissaire aux comptes, formerly of KPMG and Deloitte. The firm serves SMEs, startups, independent professionals and real estate investors across France, in French and in English.