Ireland's Corporate Tax System is a central component of Ireland's economy. In 2016–17, foreign firms paid 80% of Irish corporate tax, employed 25% of the Irish labour force, and created 57% of Irish OECD non-farm value-add. As of 2017, 25 of the top 50 Irish firms were U.S.–controlled businesses, representing 70% of the revenue of the top 50 Irish firms. By 2018, Ireland had received the most U.S. § Corporate tax inversions in history, and Apple was over one–fifth of Irish GDP. Academics rank Ireland as the largest tax haven; larger than the Caribbean tax haven system.

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.