Preparations to take part in the European elections on 23 May began after the EU agreed a Brexit delay until the end of October.
The government had hoped a Brexit deal would be done by then, and Theresa May said the UK would not have to take part if MPs agreed a Brexit plan first.
But now the UK will definitely take part in the elections, returning 73 Members of the European Parliament (MEPs) to Brussels and Strasbourg.
This election happens every five years in EU countries.
Who can vote in the EU elections in the UK?
Voters must be registered to vote, be 18 years old or over on 23 May, be a British, Irish or qualifying Commonwealth citizen or a citizen of an EU country.
You have to be resident at a UK address (or a British citizen living abroad who has been registered to vote in the UK in the last 15 years) and not be legally excluded from voting.
How can I register to vote?
You must register to vote to have your say. The deadline to register for the EU elections is Tuesday, 7 May.
Voters can register online and may need a National Insurance number or passport details to do so.
What about EU citizens resident in the UK?
If you are a citizen of an EU country and are resident in the UK, you can vote either in the UK or in your home country.
To vote in England, Wales or Scotland you must register online and complete a form stating that you wish to vote in the UK, not your home country, and send it to your local electoral registration office.
EU citizens in Northern Ireland must register online and complete an EC6 registration form before Tuesday, 7 May.
How do the European parliamentary elections work?
Voters will choose 73 MEPs in 12 multi-member regional constituencies.
Each region has a different number of MEPs based on its population.
The constituencies are:
- East Midlands (five MEPs)
- East of England (seven)
- London (eight)
- North East (three)
- North West (eight)
- Northern Ireland (three)
- Scotland (six)
- South East (10)
- South West (six)
- Wales (four)
- West Midlands (seven)
- Yorkshire and the Humber (six)
MEPs are elected by proportional representation, in order as listed by their party.
The number of MEPs each party gets is calculated using a formula called d’Hondt (a type of proportional representation), except in Northern Ireland, where the Single Transferable Vote (STV) system is used (meaning that voters are able to rank the candidates in order of preference).
Which parties are standing?
We have a guide here on what we know so far about how the main parties are preparing for the 23 May polls.
You can access a list of candidates here.
When can I vote?
The election is due to place on 23 May, between 07:00 and 22:00 BST.
When will I know the result?
Results are expected from 22:00 BST on Sunday, 26 May.
Preparations to take part in the European elections on 23 May began after the EU agreed a Brexit delay until the end of October. The government had hoped a Brexit deal would be done by then, and Theresa May said the UK would not have to take part if MPs agreed a Brexit plan first.