Tens of millions of voters are expected to have their say in the referendum on the UK's membership of the EU on 23 June. The historic ballot, decades after Britain's 1975 referendum on the European Economic Community (EEC), will see polling places open across the UK and Gibraltar from 7am until 10pm BST (EU referendum: follow our live blog).
Voters aged 18 and over, including Irish citizens registered to vote, will be asked a simple question: "Should the United Kingdom remain a member of the European Union or leave the European Union?". People who have already applied to vote via proxy or a postal ballot will have also had to submit their form by 10pm.
The 382 council areas in the United Kingdom, including one for Northern Ireland and one for Gibraltar, will begin counting the votes once polls have closed.
The first to declare is expected to be Sunderland, a feat the area has achieved at numerous general elections, while other authorities are expected to announce around 7am.
The ballot papers from local areas will be sent to 12 regional centres. Counting officers will collate the local totals in their electoral region into a total and submit the number to the chief counting officer, who will be based at Manchester Town Hall.
A picture of the EU referendum result will begin to form around 4am, while the chief counting officer will make a formal nationwide declaration at "breakfast time" once all regional totals, and the total for Northern Ireland have been approved and declared, according to the Electoral Commission.
Unlike general elections, there will be no official exit poll for the referendum. However, some UK hedge funds have commissioned their own private polls. Once the result is announced on 24 June, the Prime Minister David Cameron, who called the referendum, is expected to address the nation outside Number 10.