Voting systems in the UK

Voting systems, or electoral systems, are the method by which we elect representatives. A voting system determines the rules on how we elect parties and candidates.

The House of Commons, Scottish Parliament, Welsh Parliament, Northern Ireland Assembly and UK local authorities use different voting systems.

First-past-the-post

The House of Commons, mayoral elections in England, Police and Crime Commissioner elections and local councils in England and Wales use the first-past-the-post system.

Voters select their preferred candidate. The candidate with the most votes wins.

Alternative Vote (AV)

Alternative Vote is used to elect:

chairs of most committees in the House of Commons
the Lord Speaker and by-elections for hereditary peers.

Voters rank candidates in order of preference by marking 1, 2, 3 and so on. A voter can rank as many or as few candidates as they like or vote for one candidate.

First preference votes are counted first. If a candidate receives more than 50 per cent of the first preference votes then they are elected.

If no candidate reaches 50 per cent, the candidate with the fewest first preference votes is eliminated. Their second preference votes are reallocated to the remaining candidates. If one candidate has more votes than the other remaining candidates put together, that candidate is elected.

If not, the process is repeated until one candidate has more votes than the other remaining candidates put together. This candidate wins the election.

Supplementary Vote (SV)

The SV system is like the AV system. Voters are limited to a first and second preference choice. A voter marks a cross in one column for their first preference candidate. They mark another cross in a second column for their second preference if they wish to do so.

If a candidate receives more than 50 per cent of the first preference votes then they are elected.

If no candidate reaches the 50 per cent threshold, the two candidates with the highest number of votes remain. This eliminates the other candidates. The second preferences of voters who voted for eliminated candidates are then counted. Any made for the two remaining candidates are transferred. The candidate with the most votes at the end of this process is elected.

Up until May 2023, elections for mayors in England and for Police and Crime Commissioners in England and Wales, used SV.

Single Transferable Vote (STV)

Single Transferable Vote is used for:

Elections for Deputy Speakers in the House of Commons
Northern Ireland Assembly elections
Local elections in Scotland and Northern Ireland

STV was also used in Northern Ireland to elect Members of the European Parliament from 1979 to 2019.

Constituencies which elect more than one representative use STV.

Voters rank candidates in order of preference by marking 1, 2, 3 and so on. A voter can rank as many or as few candidates as they like or vote for only one candidate.

Each candidate needs to reach a quota. This is the minimum number of votes calculated according to the number of seats and votes cast.

The first preference votes for each candidate are added up. Candidates who achieve this quota are elected.

Surplus votes from candidates who hit the quota go to second preference candidates.

The candidate with the fewest first preference votes who do not achieve the quota are eliminated. Voters who voted for an eliminated candidate then have their votes transferred to their second preference. The process of transferring surpluses and second (or third, fourth, and so on) preferences continues until all vacant seats have been filled.

Additional Member System (AMS)

The Additional Member System is used by:

the Scottish Parliament
the Welsh Parliament
the London Assembly

Voters are given two votes on separate ballot papers. One vote is for a constituency member and one vote is for a party list. In Scotland and Wales list members are elected by region. In London there is a single London-wide list.

Constituency votes are counted first and the members for each constituency are elected using first-past-the-post.

Additional members are then elected by counting the party list votes in each region. The number of members elected from the list is based on the percentage of the votes cast but also takes into account the number of constituency members already elected in the region. This is designed to make the result more proportional to the number of votes cast.

Closed Party List

The Closed Party List system was used in England, Scotland and Wales to elect Members of the European Parliament between 1999 and 2019.

Under this system, a voter marks a cross on the ballot paper next to the party's name. Parties get the number of seats in proportion to the votes it receives in each constituency.

Voters choose parties not candidates. The parties determine the order in which candidates appear on the list.

Related information

Parliament and constitution research

Read House of Commons Library briefing papers to find out more information about voting systems in the UK.

Second ballot

Under the Second Ballot system a first-past-the-post election is held. If no candidate gets more than 50 per cent of the vote, the candidates who fail to reach a specified threshold are eliminated.

A second election is held (usually several days later) and the candidate who receives the most votes in this second ballot is elected.

Limited vote

Limited Vote systems use multi-member constituencies. Voters, however, have fewer votes than there are available seats.

An electoral system used in multi-member constituencies in which electors have more than one vote, but fewer votes than there are candidates to be elected. The candidates with the most votes are elected.