If you have ever looked at the financial statements of a major corporation, followed a large merger, or wondered who audits the world’s biggest companies, you have probably encountered four names: Deloitte, PwC, EY and KPMG.
Together, they are known as the Big Four — the world’s largest professional services networks. Their roots are in accounting and auditing, but they now also advise companies on taxes, transactions, technology, cybersecurity, risk and strategy.
Why Are They Called the Big Four?
The name is straightforward: four firms dominate the global professional-services and accounting industry.
They are:
- Deloitte
- PwC
- EY
- KPMG
The firms operate through legally independent member firms in different countries. They are better understood as global professional-services networks than as conventional multinational corporations.
What Do They Do?
The Big Four began with auditing: examining financial statements and providing an independent opinion on their accuracy.
Today, their services generally include:
- Audit and assurance
- Tax
- Consulting and advisory
- Mergers and acquisitions
- Risk and cybersecurity
- Technology and business transformation
This expansion turned them from accounting firms into broad business-services organizations.
Deloitte: A Brief Profile
Deloitte is one of the oldest and largest professional-services networks in the world. Its origins date back to 1845, when William Welch Deloitte opened an office in London.
The firm provides audit, consulting, tax, financial advisory and risk services. It is especially known for helping large organizations with technology implementation, digital transformation, cybersecurity, regulatory compliance and business strategy.
Its main clients include multinational corporations, banks, insurance companies, technology companies, governments and public-sector organizations. Deloitte generally does not publish a complete global client list, and its clients vary by country and business division.
PwC: A Brief Profile
PwC, short for PricewaterhouseCoopers, was created in 1998 through the merger of Price Waterhouse and Coopers & Lybrand. Its history, however, goes back much further through the predecessor firms.
PwC focuses on audit and assurance, tax, consulting, deals and business transformation. It advises companies on financial reporting, transactions, technology, cybersecurity, sustainability and regulatory issues.
Its main clients include global banks, pharmaceutical companies, manufacturers, retailers, energy companies, technology firms and governments. PwC also works with private-equity investors and companies involved in mergers, acquisitions and restructuring.
EY: A Brief Profile
EY, formerly Ernst & Young, was formed in 1989 through the merger of Ernst & Whinney and Arthur Young. The firm operates as a global network of independent member firms.
Its main areas include audit, tax, consulting and strategy and transactions. EY is particularly active in advising companies on mergers and acquisitions, corporate strategy, risk management, technology and financial transformation.
Its main clients include multinational corporations, financial institutions, technology companies, consumer-goods businesses, industrial groups, governments and private-equity firms. As with the other Big Four networks, specific clients differ by country and service line.
KPMG: A Brief Profile
KPMG is a global professional-services network whose modern structure was created in 1987 through the merger of Peat Marwick International and Klynveld Main Goerdeler.
The firm provides audit, tax and advisory services. Its work includes risk management, regulatory compliance, cybersecurity, restructuring, technology, transactions and operational improvement.
KPMG’s main clients include banks, insurers, industrial companies, energy businesses, healthcare organizations, retailers, governments and large privately held companies. It also advises investors and companies involved in acquisitions, restructuring and financial reporting.
From the Big Eight to the Big Four
The modern Big Four emerged through decades of consolidation.
In 1989, mergers reduced the Big Eight to six firms. In 1998, Price Waterhouse and Coopers & Lybrand merged to create PwC.
Then, in 2001, energy company Enron collapsed after revelations of accounting irregularities. Its auditor, Arthur Andersen, was convicted of obstruction of justice and soon disappeared as a major global audit firm.
The industry had gone from eight major firms to four:
Deloitte, PwC, EY and KPMG.
Why Does Audit Matter?
Auditing helps create trust in financial information.
Investors, banks, regulators, employees and suppliers all rely on company reports when making decisions. Although auditors are paid by the companies they audit, their work is intended to provide confidence to shareholders and other users of financial statements.
That is why independence and objectivity are central to the profession.
Why Do Companies Hire Them for Consulting?
A company may hire a Big Four firm for an audit and later seek help with other challenges, such as:
- Restructuring tax operations
- Implementing regulatory systems
- Redesigning supply chains
- Evaluating an acquisition
- Managing cybersecurity
- Leading a digital transformation
This overlap has brought the Big Four into competition with traditional consulting firms such as McKinsey, BCG and Bain.
The difference is historical: the Big Four grew from accounting, auditing and tax, while traditional strategy firms began with management consulting.
The Big Four in the Age of AI
Artificial intelligence is changing professional services.
AI can analyze financial data, accelerate tax research, review documents and automate repetitive consulting work. This creates opportunities, but it also challenges a business model built around large numbers of professionals performing knowledge-intensive tasks.
The Big Four will increasingly compete on more than labor. Expertise, technology and professional judgment may become even more important.
The Bigger Picture
The Big Four are more than accounting firms.
They audit companies, advise governments, support transactions, manage tax complexity, investigate risk and help organizations transform their operations.
Their main clients are typically large corporations, financial institutions, governments, public-sector bodies, private-equity investors and multinational organizations. However, each firm also serves medium-sized businesses, entrepreneurs and nonprofit organizations through its local member firms.
Their rise reflects the globalization of business. As companies became larger and more international, they needed institutions capable of creating trust and transferring specialized knowledge across borders.
The accounting firm evolved into the professional-services network.
And four names came to dominate that system:
Deloitte, PwC, EY and KPMG.
