Tens of millions of people are expected to take part in arguably the most important vote in a generation on 23 June. The EU referendum will see the electorate choose whether they want to Remain or Leave the 28-nation-bloc.
A similar vote was held in 1975 when the British electorate were asked whether they wanted to stay in or quit the European Economic Community (EEC), known as the Common Market.
Who can vote?
British citizens living in the UK aged 18 and over on 23 June will be able to vote.
EU citizens will not be able to have a say unless they are an Irish citizen living in the UK, or Commonwealth citizen in the UK, who has permission to remain in the UK, or who does not require leave to remain in the UK.
British citizens living overseas, who have been registered to vote in the UK in the last 15 years, are also eligible.
How to register
To apply to vote by post in England, Scotland or Wales, you need to complete a postal vote application form (found here) and send it to your local electoral registration office.
The deadline to apply for a postal vote in Northern Ireland has passed.
If you want someone to vote for you, known as a proxy vote, you need to apply by 5pm on 15 June. Like the postal application, you will have to complete a form (found here) and send it to your local electoral registration office.
Where to vote
Polling places will be open across the UK between 7am and 10pm on 23 June. A polling card should be sent to you address after you have registered. It will tell you where to find your polling station. You can also find your polling station by typing in your post code here.
You do not need the polling card to vote. However, in Northern Ireland you will need a correct form of photo ID.
How to fill out the ballot
Select your choice by putting a cross (X) in the Remain or Leave box on the paper. Your ballot paper is likely to be spoiled if you put a cross in both boxes.