UK parliamentary by-elections since 1945
This list notes the number of by-elections by session since 1945-46 and also lists the successful candidate in by-elections since 2005.

Constituencies are reviewed periodically by independent Boundary Commissions, one for each part of the UK. This briefing outlines how the public can get involved in the consultation stages.
Parliamentary boundary reviews: public consultations (888 KB , PDF)
UK Parliamentary constituency boundaries are reviewed periodically to take account of population changes. Reviews are carried out by four Boundary Commissions, one for each part of the UK.
The Commissions must follow certain rules but they also rely on public feedback to help create seats that have local support and take account of local community ties where possible. This briefing explains the public consultation process used during reviews.
The current review was formally launched on 5 January 2021. There were several stages of public consultation. The timings are a matter for each Commission but there are some statutory provisions that they must follow. They are set out in set out in the Parliamentary Constituencies Act 1986, as amended.
All the public consultation stages for the 2023 Review have now been completed. The dates are summarised below. Each of the Commissions will now consider their final recommendations, which must be handed to the Speaker of the House by 1 July 2023.
Publishing initial proposals triggered an eight-week consultation. This stage allowed people to make written representations. The initial consultations for all four Commissions have now closed. Each Commission must publish all submissions received at some point after the end of the eight weeks. Publishing these triggers the secondary consultation.
These were held in the spring of 2022. The consultation period ran for six weeks and representations could include comments on submissions from the initial consultation.
The secondary period included public hearings. There must be at least two and no more than five per region of England, lasting up to two days. Scotland, Wales and Northern Ireland also had each had to at least two and no more than five hearings. They also could last up to two days.
After the secondary consultation period, each Commission must publish any written submissions and transcripts of the public hearings.
If a Commission decides to publish revised proposals as a result of representations received in the first two consultation periods, this triggers a third consultation.
This lasted four weeks and there were no public hearings.
Anyone can make a submission during a consultation period. This includes MPs but they must make submissions the same way as everyone else.
A Commission will give equal consideration to each submission regardless of how it is submitted. This could be a presentation at a public hearing or a written submission. Written submissions can be electronic or hard copy but people are encouraged to respond via the review websites each Commission provides.
The Commissions encourage people to say whether they agree or disagree with proposals. If someone disagrees, they are encouraged to suggest alternative proposals.
The Commissions will publish more details on their websites:
Boundary Commission for England
Boundary Commission for Scotland
Boundary Commission for Northern Ireland
There is more information on the background to boundary reviews and the number of Members of Parliament in the Library briefing Constituency boundary reviews and the number of MPs (SN05929).
Parliamentary boundary reviews: public consultations (888 KB , PDF)
This list notes the number of by-elections by session since 1945-46 and also lists the successful candidate in by-elections since 2005.
This note explains the supply and sale of the full and open versions of the electoral register.
The UK has 14 Overseas Territories. What are they, and what is their relationship with the UK?