Deloitte

Deloitte is the largest professional services network in the world, a position it has held for years by both revenue and headcount. The firm's roots go back to 1845, when William Welch Deloitte, a 27-year-old accountant, opened a practice on Basinghall Street in London. That same year, the Institute of Chartered Accountants in England and Wales was founded, and Deloitte's firm quickly became a fixture in the emerging profession. The company expanded to the United States in 1890, setting the stage for a century of growth through mergers and acquisitions.

Modern Deloitte took shape through a series of key combinations. The 1952 merger with Haskins & Sells brought a major American accounting practice into the fold. Then, in 1989, Deloitte Haskins & Sells merged with Touche Ross to create Deloitte & Touche. The international arm was renamed Deloitte Touche Tohmatsu in 1993, later shortened to simply Deloitte. A pivotal moment came in 2002, when Deloitte absorbed large parts of Arthur Andersen's practice in the UK, Europe, and the Americas after Andersen's collapse in the Enron scandal. That move dramatically expanded Deloitte's client base and market share. In 2013, the firm acquired Monitor Group, a strategy consulting firm co-founded by Harvard professor Michael Porter, strengthening its consulting offerings.

Today, Deloitte operates as a Swiss verein, legally named Deloitte Touche Tohmatsu Limited, with member firms in over 150 countries. The network employs roughly 470,000 people and serves nearly 90% of the Fortune 500, along with more than 9,000 US-based private companies. In fiscal year 2024, it reported $67.2 billion in aggregate global revenues. Deloitte's four main business lines are audit and assurance, consulting, tax and legal, and financial advisory. A specialized arm, Deloitte Digital, combines creative agency capabilities with technology consulting to deliver AI-enabled content and digital marketing solutions. [edit]