There is no single electoral system used for every election in the United Kingdom. The system depends on which institution is being elected.
House of Commons — First Past the Post
UK general elections use First Past the Post. Each constituency elects one MP and the candidate with the most votes wins.
Scottish Parliament — Additional Member System
Holyrood combines 73 constituency MSPs with 56 regional MSPs. Each voter has two votes. The regional element is used to make representation more proportional than the constituency results alone.
Senedd — closed proportional list
From 2026, Wales elects 96 Senedd Members from 16 six-member constituencies. Voters cast one vote for a party or independent candidate, and seats are allocated proportionally within each constituency.
Northern Ireland Assembly — STV
Northern Ireland uses the Single Transferable Vote. Each of 18 constituencies elects five MLAs and voters rank candidates in preference order.
Why this matters when reading results
A 30% vote share does not have the same mechanical effect under every system. FPTP selects one constituency winner; proportional and multi-member systems translate votes into representation differently.
That also means terms such as vote share, swing, majority and tactical voting need to be interpreted in the context of the electoral system being used.
Further reading
UK Parliament: voting systems ↗ · Scotland · Wales · Northern Ireland