Ernst & Young Global Limited, commonly known as Ernst & Young or simply EY, is a multinational professional services network with headquarters in London, England. EY is one of the largest professional services networks in the world. Along with Deloitte, KPMG and PricewaterhouseCoopers, it is considered one of the Big Four accounting firms. It primarily provides assurance (which includes financial audit), tax, consulting and advisory services to its clients. Like many of the larger accounting firms in recent years, EY has expanded into markets adjacent to accounting, including strategy, operations, HR, technology, and financial services consulting.