The agreement was signed in London on 6 December 1921, by representatives of the British government (which included Prime Minister David Lloyd George, who was head of the British delegates) and by representatives of the Irish Republic including Michael Collins and Arthur Griffith. The Irish representatives had plenipotentiary status (negotiators empowered to sign a treaty without reference back to their superiors) acting on behalf of the Irish Republic, though the British government declined to recognise that status. As required by its terms, the agreement was approved by "a meeting" of the members elected to sit in the House of Commons of Southern Ireland and [separately] by the British Parliament. In reality, Dáil Éireann (the legislative assembly for the de facto Irish Republic) first debated then approved the treaty; members then went ahead with the "meeting". Though the treaty was narrowly approved, the split led to the Irish Civil War, which was won by the pro-treaty side.
The Irish Free State as contemplated by the treaty came into existence when its constitution became law on 6 December 1922 by a royal proclamation.
As with the other dominions, the King would be the Head of State of the Irish Free State (Saorstát Éireann) and would be represented by a Governor General (See Representative of the Crown).
Members of the new free state's parliament would be required to take an Oath of Allegiance to the Irish Free State. A secondary part of the oath was to "be faithful to His Majesty King George V, His heirs and successors by law, in virtue of the common citizenship".