Ernst & Young (trading as EY) is a multinational professional services firm headquartered in London, United Kingdom. It is one of the "Big Four" audit firms and is the third largest professional services firm in the world by aggregated revenue in 2014, after PwC and Deloitte.
The organization operates as a network of member firms which are separate legal entities in individual countries. It has 212,000 employees in over 700 offices around 150 countries in the world. It provides assurance (including financial audit), tax, consulting and advisory services to companies.
The firm dates back to 1849 with the founding of Harding & Pullein in England. The current firm was formed by a merger of Ernst & Whinney and Arthur Young & Co. in 1989. It was known as Ernst & Young until 2013, when it underwent a re-branding to EY. The acronym "EY" was already an informal name for the firm prior to its official adoption.