Deloitte Touche Tohmatsu Limited, commonly referred to as Deloitte, is an international professional services network headquartered in London, United Kingdom. Deloitte is the largest professional services network by revenue and number of professionals in the world and is considered one of the Big Four accounting firms along with EY, KPMG, and PricewaterhouseCoopers.
The firm was founded by William Welch Deloitte in London in 1845 and expanded into the United States in 1890. It merged with Haskins & Sells to form Deloitte Haskins & Sells in 1972 and with Touche Ross in the US to form Deloitte & Touche in 1989. In 1993, the international firm was renamed Deloitte Touche Tohmatsu, later abbreviated to Deloitte. In 2002, Arthur Andersen’s practice in the UK as well as several of that firm’s practices in Europe and North and South America agreed to merge with Deloitte.
Deloitte provides audit, consulting, financial advisory, risk advisory, tax, and legal services with approximately 334,800 professionals globally. In FY 2021, the network earned revenues of US$50.2 billion in aggregate. As of 2020, Deloitte is the third-largest privately-owned company in the United States, according to Forbes. The firm has sponsored many activities and events, including the 2012 Summer Olympics.