The Fifth Schedule to this act provided the constituencies for the House of Commons in these two separate parliaments.

Only the Dublin University MPs attended for the intended first meeting of the House of Commons of Southern Ireland, with those elected for Sinn Féin sitting as TDs in Dáil Éireann.

This included the Pro-Treaty Sinn Féin TDs and the four representatives of Dublin University.

Under the terms of the Treaty, the Irish Free State left the United Kingdom on 6 December 1922.

In the House of Commons of Northern Ireland, the constituencies were replaced under the House of Commons (Method of Voting and Redistribution of Seats) Act (Northern Ireland) 1929 with single-seat constituencies elected by first-past-the-post voting.