1833 – Deloitte starts all the way back in 1833 when its founder William Welch Deloitte first became an accountant.
1845 – Deloitte was founded in 1845 by William Welch Deloitte. He opened the first Deloitte office in London, UK. The name of the firm Deloitte is derived from William Welch Deloitte’s last name. William Welch Deloitte was the first accountant to be appointed as an independent auditor of a public company. That company was the Great Western Railway.
1857 – Deloitte’s first partnership with another accountant, Thomas Greenwood, was in 1857. The firm changed its name to Deloitte and Greenwood.
1880 – Deloitte formed his first office in New York in 1880.
1898 – George Touche founded his own firm in London. In 1911,
1911 – George Touch opened Touche Niven & Co. in New York City.
1905 – Deloitte collaborated with Haskins & Sells for the first time. The two would later merge.
1933 – Deloitte was instrumental in convincing the United States Congress that independent audits of public companies was vital to the financial economy.
1952 – Deloitte merged with Haskins & Sells in 1952 to become Deloitte Haskins & Sells.
1960 – Touche, Ross, Bailey and Smart was founded in 1960 through a merger between Canadian and UK firms.
1968 – One of Deloitte’s member firms, Tohmatsu Awoki & Co, was founded in 1968.
1972 – The chairman of Touche Ross which is one of Deloitte’s founding firms helped establish the Financial Accounting Standards Board in 1972 (FASB).
1978 – The name Deloitte Haskins and Sells was adopted.
1989 – Deloitte as we know it today emerged from the merger of Deloitte Haskins & Sells and Touche Ross in 1989.
1997 – Deloitte.com was launched.
2003 – Deloitte established a single brand in 2003.
2017 – Deloitte is the largest professional services firm if you rank the big 4 accounting firms by revenue.