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 Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps).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.
Partition of Ireland
Soon after the end of the war Sinn Féin won the overwhelming majority of the Irish parliamentary seats in the UK general election of 1918, and in January 1919 the Sinn Féin members declared unilaterally an independent (all-island) Irish Republic. Unionists, however, won a majority of seats in four of the nine counties of Ulster and affirmed their continuing loyalty to the United Kingdom. Following the Paris Peace Conference, in September 1919 Lloyd George tasked the "Long Committee" to implement Britain's commitment to introduce Home Rule, which was based on the policy of Walter Long, and some findings of the Irish Convention. The result was to be two home-rule Irish jurisdictions, and in November 1920 the Government of Ireland Act 1920 was enacted. As a result of this, in April 1921 the island was partitioned into Southern and Northern Ireland.