MPs cannot directly resign their seat. The only means by which an MP can leave during the lifetime of a Parliament is through death; expulsion by resolution of the House; or disqualification.

This means Douglas Carswell will have to accept one of a number of offices which are incompatible with membership of the House of Commons.

Tradition dictates that the Chancellor of the Exchequer grants either the Chiltern Hundreds or the Manor of Northstead by means of a written warrant.

The MP retains the position until the Chancellor appoints another applicant or until the holder applies for release from it.

The custom of using the Chiltern Hundreds is believed to have originated around 1750, whilst the first recorded use of the Manor of Northstead for this purpose is by Patrick Chalmers, in 1844. Since 1850, applications have been registered and retained in the Treasury. On the day the warrant is signed a letter is sent to the Member, omitting the letters MP after his name, to inform him that he has been appointed to the office. Letters of notification are also sent at the same time to the office of the Speaker, and the Government and opposition whips. The appointment is noted in the London Gazette, and the Treasury issues a brief press notice.

The holder of the office is not prevented from standing for re-election.