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 The latter were withdrawn soon afterwards upon the establishment of the Provisional Government, but the former continued to issue revenue stamps until the late 20th century.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.
Irish Republic
The War of Independence ended with the Anglo-Irish Treaty, signed on 6 December 1921 and narrowly approved by Dáil Éireann on 7 January 1922. A Provisional Government was set up under the terms of the treaty, but the Irish Republic nominally remained in existence until 6 December 1922, when 26 of the island's 32 counties became a self-governing British Dominion called the Irish Free State. The island had been partitioned by the Government of Ireland Act 1920, and the six counties of Northern Ireland exercised their right under the Treaty to opt out of the Free State, and remain in the United Kingdom.