The Double Irish arrangement was a base erosion and profit shifting (BEPS) corporate tax avoidance tool used mainly by United States multinationals since the late 1980s to avoid corporate taxation on non-US profits. (The US was one of a small number of countries that did not use a "territorial" tax system, and taxed corporations on all profits, no matter whether the profit was made outside the US or not, in contrast to "territorial" tax systems which tax only profits made within that country.) It was the largest tax avoidance tool in history. By 2010, it 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.
Despite US knowledge of the Double Irish for a decade, it was the European Commission that in October 2014 forced Ireland to close the scheme, starting in January 2015. However, users of existing schemes, such as Apple, Google, Facebook and Pfizer, were given until January 2020 to close them. At the announcement of the closure, it was known that multinationals had replacement BEPS tools in Ireland, the Single Malt (2014), and Capital Allowances for Intangible Assets (CAIA) (2009):