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 The latter were withdrawn soon afterwards upon the establishment of the Provisional Government, but the former continued to issue revenue stamps until the late 20th century.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.
Royal and Parliamentary Titles Act 1927
As a result of the Anglo-Irish Treaty, in 1922 most of Ireland was detached from the United Kingdom of Great Britain and Ireland to become the Irish Free State. However, six north-eastern counties remained united with Great Britain as Northern Ireland.