Deloitte grew from one London accountant into the world's largest professional services network
When the Great Western Railway needed someone to check its books, William Welch Deloitte became the first person appointed as an independent auditor of a public company. He had opened an office on Basinghall Street in 1845. His firm now employs roughly 470,000 people and earned 67.2 billion US dollars in 2024.
Expansion abroad began in 1890 with a branch on Wall Street, run by Edward Adams and P.D. Griffiths, soon followed by Chicago and Buenos Aires. Across the Atlantic, Charles Waldo Haskins and Elijah Watt Sells founded Haskins & Sells in New York in 1896, a major auditing house built by American rather than British accountants. One of its managing partners, Arthur Hazelton Carter, helped persuade the US Congress in 1933 that public companies should face mandatory independent audits.
The modern name is a stack of mergers. Deloitte's London firm joined Haskins & Sells in 1952. George Touche's network, meanwhile, grew into Touche Ross and in 1975 absorbed a Japanese practice founded by Nobuzo Tohmatsu. When Deloitte Haskins & Sells and Touche Ross combined in the US in 1989, the UK arm refused and went to Coopers & Lybrand instead, so the global firm briefly traded as DRT International before becoming Deloitte Touche Tohmatsu in 1993.
Acquisitions widened the business well beyond accounting. After the collapse of Arthur Andersen, its UK practice and several others joined in 2002. Deloitte bought Beijing Pan-China CPA in 2005 to become China's biggest accountancy, took over Monitor Group, the strategy consultancy founded by Michael Porter, in 2013, and built a digital agency that billed 2.1 billion dollars in 2015. It even opened a blockchain lab in Dublin in 2016.
Today it offers audit, tax, consulting, risk, legal and financial advice in more than 150 countries as one of the Big Four, alongside EY, KPMG and PwC. The firm has faced lawsuits over some audits and suffered a serious cyberattack in 2017, yet it keeps appearing on Fortune's list of the best companies to work for.
Source: Deloitte
