Revenue stamps of the United Kingdom
When Ireland was partitioned into Northern Ireland and Southern Ireland in 1921, separate revenue stamps were issued for both entities. Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps). However, Northern Ireland continued to use separate revenue stamps until the 1980s. Northern Irish revenues include Civil Service, Dog Licence, Excise and National Insurance stamps, among many others.
Irish Boundary Commission
The Government of Ireland Act 1920 was enacted during the height of the War of Independence and partitioned the island into two separate Home Rule territories of the United Kingdom of Great Britain and Ireland, to be called Northern Ireland and Southern Ireland. In its determination of this border, the Parliament of the United Kingdom heard the arguments of the Irish Unionist Party, but not those of most of the elected representatives of the Irish nationalist population. Sinn Féin refused to recognise any legitimate role of that Parliament in Irish affairs and declined to attend it, leaving only the Irish Parliamentary Party, whose representation at Westminster had been reduced to miniscule size at the 1918 General Election, present at the debates. James Craig's brother told the British House of Commons unambiguously that the six northeastern counties were the largest possible area that unionists could "hold".