Unless Theresa May can get her Brexit withdrawal agreement approved by parliament beforehand, the UK will be holding European parliamentary elections on Thursday 23 May 2019.

Here’s all you need to know about whether you can vote, and how to register:

Who can vote in EU elections?

To vote in May’s election you must be registered to vote, be 18 or over on 23 May, be a British, Irish, or qualifying Commonwealth citizen, or a citizen of an EU country. You have to be either resident at an address in the UK, and not be legally excluded from voting – or be a British citizen living abroad, in which case you can vote in European elections for up to 15 years after you have left the country.

If you are not already on the electoral roll, you can register to vote online whether you are resident in the UK or a UK citizen abroad. You may need your national insurance or passport number.

EU citizens resident in the UK need to fill in an extra form

Unlike the Brexit referendum, EU citizens resident in the UK can vote in European parliamentary elections.

If you are a citizen of an EU country (other than the UK, Ireland, Malta and Cyprus) resident in England, Scotland or Wales, to vote you must do the following three things by Tuesday 7 May:

Be registered to vote. You can register online here .

Download the European parliament voter registration form here .

Send the completed form to your local Electoral Registration Office, whose address you can find here.

If you are a citizen of an EU country (other than the UK, Ireland, Malta and Cyprus) resident in Northern Ireland, you must do the following three things by 7 May:

Be registered to vote. You can register online here .

Download the European parliament voter registration form EC6 from the Electoral Office for Northern Ireland here .

Send the completed form to reach The Electoral Office for NI, 2nd floor, St Anne’s House, 15 Church Street, Belfast BT1 1ER by Tuesday 7 May.

Citizens from the UK, Ireland, Malta and Cyprus are not require to fill in the additional form.

How do European parliamentary elections work?

The UK elects 73 members (MEPs) to the European parliament, which is made up of 751 MEPs elected by the 28 member states of the EU. The UK is split into 12 European electoral regions, and each region is represented by between three and 10 MEPs.

The constituencies are:

South East England (10 MEPs)

London (8)

North West England (8)

East of England (7)

West Midlands (7)

South West England (including Gibraltar) (6)

Yorkshire and the Humber (6)

Scotland (6)

East Midlands (5)

Wales (4)

North East England (3)

Northern Ireland (3)

You can find out who is standing for election in your area here.

In England, Scotland and Wales, voters can choose to vote for one party or individual. The D’Hondt method of proportional representation is used to calculate how many seats each party or individual receives. MEPs are then elected from closed lists of candidates supplied by the parties.

In Northern Ireland, the single transferable vote method is used, where each voter ranks candidates in order of preference, marking 1 beside their most preferred candidate, 2 beside their second choice, and so on. These votes are then used to allocate Northern Ireland’s three MEPs.

Those elected as MEPs on 23 May will represent the UK when the new European parliament assembles on 1 July, until such time as the UK ceases to be a member of the European Union.