Revenue stamps of Northern Ireland
Upon the partition of Ireland in 1921, separate revenue stamps began to be issued for both Northern Ireland and Southern Ireland. The latter were withdrawn soon afterwards upon the establishment of the Provisional Government, but the former continued to issue revenue stamps until the late 20th century. The need for separate issues for Northern Ireland came about since taxes raised there were meant to remain in the country. Most Northern Irish revenue stamps were British key types with appropriate inscriptions, but there were a number of different issues as well.
Republic of Ireland
In the Northern Ireland question, the British and Irish governments started to seek a peaceful resolution to the violent conflict involving many paramilitaries and the British Army in Northern Ireland known as "The Troubles". A peace settlement for Northern Ireland, known as the Good Friday Agreement, was approved in 1998 in referendums north and south of the border. As part of the peace settlement, the territorial claim to Northern Ireland in Articles 2 and 3 of the Constitution of Ireland was removed by referendum. In its white paper on Brexit the United Kingdom government reiterated its commitment to the Good Friday Agreement. With regard to Northern Ireland's status, it said that the UK Government's "clearly-stated preference is to retain Northern Ireland’s current constitutional position: as part of the UK, but with strong links to Ireland".