Parliamentary constituency boundaries are reviewed periodically by independent Boundary Commissions. This House of Commons Library briefing summarises the current rules and procedures for boundary changes and how they have changed over time. It also gives an overview how the number of MPs has reached the current number.

The Armed Forces can register to vote as ordinary electors, as overseas voters, or as service voters. There has been concern about the under-registration of the Armed Forces, especially those serving overseas, and the difficulties they face in participating in the electoral process more generally.The Note also gives a brief history of how the system of voting by members of the Armed Forces has changed, particularly during the periods directly after each World War.