The oath that is taken in the House of Commons swears allegiance to the Crown. Members are sworn in after a general election, by-election or after the death of the Monarch. Members have the choice to take the oath or make a solemn affirmation and they can choose the sacred text they wish to use. After the oath or affirmation is taken, the MP will sign their name in a book made of parchment called the “Test Roll.” The MP is then introduced by the House of Commons Clerk to the Commons Speaker.
Since the death of our Monarch, Queen Elizabeth II, MPs have retaken the oath to swear their allegiance to the newly crowned Monarch, King Charles III. Long live the King.
If you would like further information about oaths, please follow this link: https://www.parliament.uk/about/how/elections-and-voting/swearingin/