A marathon counting session will get under way when polls close tonight - with more than 6,000 results to be declared in a process that will stretch on for two days or more.
After a continuous 24-hour stream of counts and results through to late Friday - and perhaps a brief pause - counting will resume on Saturday morning in Northern Ireland.
The STV (single transferable vote) system in use can involve as many as 15 rounds in a constituency, with the process lasting towards midnight and maybe even being carried over to the Monday.
The marathon timeline is:
- Thursday 22:00 - polls close, counting begins for a majority of Scottish Parliament and Welsh Assembly constituencies and just over a third of English councils;
- Friday early hours - Scottish Parliament, Welsh Assembly and English council results start to flow in;
- Friday mid-morning - As final results arrive from overnight counts, the process starts in the remaining constituencies and councils;
- Friday early afternoon - The final outcome may be known in Scotland and Wales but the counting goes on in many councils and gets under way in Northern Ireland;
- Friday 16:00 - Counting starts in the Alternative Vote (AV) referendum;
- Friday 21:00 - The referendum results could be complete but some council results involving recounts could still be awaited. Counting will have been adjourned in most Northern Ireland constituencies except possibly a handful where electoral staff are close to finishing;
- Saturday 09:00 - Counting resumes in Northern Ireland;
- Saturday 23:59 - Northern Ireland has declared all its results or has adjourned final counting until Monday in some cases.