Deloitte

Lore & Background

He was the first person appointed independent auditor of a public company, the Great Western Railway. In 1989, Deloitte Haskins & Sells merged with Touche Ross in the US to form Deloitte & Touche. In 2002, Arthur Andersen's UK practice and several of its practices in Europe and the Americas merged with Deloitte. Subsequent acquisitions included Monitor Group, a large strategy consulting business, in 2013.

Reader's Guide

Deloitte's significance lies in its position as the world's largest professional services network by both revenue and employee count, a status achieved through a long history of mergers and expansions. The firm's legacy includes pioneering independent audits for public companies, as demonstrated by William Welch Deloitte's work for the Great Western Railway. Its growth through mergers—notably with Haskins & Sells, Touche Ross, and parts of Arthur Andersen—shaped the modern accounting industry. Its sponsorship of events like the 2012 Summer Olympics underscores its global reach.

Did You Know?

• William Welch Deloitte was the first person appointed independent auditor of a public company, the Great Western Railway.
• In 2002, Arthur Andersen's UK practice, its largest outside the US, merged with Deloitte.

Origins on Basinghall Street

William Welch Deloitte opened his accounting office on Basinghall Street in London in 1845, and within a few years made history as the first person appointed as an independent auditor of a public company, the Great Western Railway. The firm's London base shifted over the decades, settling at No. 4 Lothbury from 1855 to 1905 before relocating to No. 54 London Wall Buildings. Deloitte's vision stretched across the Atlantic when he opened a New York office in 1880, and in 1890 the firm launched its first overseas branch on Wall Street under managers Edward Adams and P.D. Griffiths, with subsequent branches in Chicago and Buenos Aires. Meanwhile, in 1896, Charles Waldo Haskins and Elijah Watt Sells founded Haskins & Sells in New York, a firm later described as the first major auditing practice established in the country by American rather than British accountants. These parallel British and American foundations would, over the following century, converge into the global network recognized today.

A Century of Mergers and Rebranding

The modern Deloitte network is the product of a long series of strategic combinations. In 1952, the London-based firm, then known as Deloitte, Plender, Griffiths & Co., joined forces with Haskins & Sells to create Deloitte Haskins & Sells. The next major leap arrived in 1989, when that entity merged with Touche Ross in the United States to form Deloitte & Touche, led jointly by J. Michael Cook and Edward A. Kangas. Not every partner agreed: a smaller group of Deloitte Haskins & Sells member firms rejected the union and instead merged with Coopers & Lybrand, eventually becoming part of PwC. The naming was itself a challenge, since key firms in the UK and Australia had not joined the merger, prompting the temporary use of DRT International before the 1993 rebrand to Deloitte Touche Tohmatsu. Later acquisitions continued the growth trajectory: Arthur Andersen's UK practice along with several European and American practices folded in during 2002, and in 2013 the firm absorbed Monitor Group, a major strategy consulting practice.

Global Scale and Service Breadth

By virtually every metric, Deloitte operates at an extraordinary scale. The network employs approximately 470,000 people across more than 150 countries, making it the largest professional services organization in the world by both revenue and headcount. In fiscal year 2024, aggregate revenues reached US$67.2 billion. The firm's service portfolio spans audit, consulting, financial advisory, risk management, tax, and legal work, all delivered through member firms of Deloitte Touche Tohmatsu Limited, a private company limited by guarantee incorporated in England and Wales. Deloitte sits alongside EY, KPMG, and PwC as one of the so-called Big Four accounting firms. Beyond its core professional work, the firm has sponsored high-profile events, including the 2012 Summer Olympics. In 2023, Deloitte ranked as the fourth-largest privately owned organization in the United States, and it has maintained a continuous presence on Fortune magazine's list of the 100 Best Companies to Work For.

Vulnerabilities and Legal Scrutiny

Despite its enormous size and reputation, Deloitte has faced significant challenges that tested its resilience. In 2017, the firm suffered a major cyberattack that resulted in a breach of client confidentiality and exposed a substantial volume of employee information to the public. The incident highlighted the risks inherent in managing sensitive data across a sprawling global network of member firms. Deloitte has also been the subject of litigation concerning several of its audits, underscoring the legal exposure that accompanies serving as an independent auditor for major public companies. These episodes sit in contrast to the firm's broader trajectory of growth and recognition, yet they remind observers that even the largest professional services network remains vulnerable to cyber threats and legal challenges. The firm's ability to absorb these shocks while continuing to rank among the world's top employers and expand its service offerings speaks to the structural depth of its member-firm model.