The Double Irish arrangement was a base erosion and profit shifting (BEPS) corporate tax avoidance tool used mostly by United States multinationals since the late 1980s to avoid corporate taxation on non-U.S. profits. It was the largest tax avoidance tool in history and by 2010 was shielding US$100 billion annually in US multinational foreign profits from taxation, and was the main tool by which US multinationals built up untaxed offshore reserves of US$1 trillion from 2004 to 2018. Traditionally, it was also used with the Dutch Sandwich BEPS tool; however, 2010 changes to tax laws in Ireland dispensed with this requirement.