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 The latter were withdrawn soon afterwards upon the establishment of the Provisional Government, but the former continued to issue revenue stamps until the late 20th century.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 Act 1948
The UK's Ireland Act also gave a legislative guarantee that Northern Ireland would continue to remain a part of the United Kingdom unless the Parliament of Northern Ireland formally expressed a wish to join a United Ireland; this "unionist veto" proved to be controversial during the Act's passage through Westminster, as well as in the Irish state and amongst Northern Ireland's nationalist community. The guarantee was replaced in 1973, when the Parliament of Northern Ireland was abolished, by a new guarantee based on "the consent of the majority of the people of Northern Ireland".