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 The latter were withdrawn soon afterwards upon the establishment of the Provisional Government, but the former continued to issue revenue stamps until the late 20th century.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.
Northern Ireland Constitution Act 1973
When the Republic of Ireland ceased to be a member of the British Commonwealth, Westminster had responded with the Ireland Act 1949. Amongst its other provisions, the Act had guaranteed that Northern Ireland would not cease to remain a part of the United Kingdom "without the consent of the Parliament of Northern Ireland" (s. 1(2)); this declaration had proven to be controversial both with the Irish government and with Northern Ireland's nationalist community.