Fact box about Britain's EU referendum

Brexit: What to expect in the first week

After a vote for Brexit, there will be calls for Prime Minister David Cameron to step down because he will have lost his Project Fear campaign to stay in the EU.

Amid rumors of a plot to oust Mr. Cameron, senior Tory MP Andrew Bridgen said, "If the country votes to leave the EU, he should – and probably will – choose to resign."

The leaders of EU member states are scheduled to meet for a summit of the European Council on Tuesday June 28 and Wednesday June 29.

The agenda for the meeting notes, "The leaders will discuss the results of the UK in/out referendum from 23 June 2016."

At this summit, Britain could trigger the EU's Article 50 - the law that would start the process of the country's political divorce from the EU.

This step would in effect start the timer on the two year-period that Britain would be given to negotiate its exit of the EU before the end of June 2018.

Eurosceptic cabinet minister Chris Grayling says that the Article 50 should not be immediately activated, but Britain should aim to quit the EU in 2019.

The EU's leaders could also call an emergency summit after a Brexit vote; while Spanish citizens are due to go to the polls in a general election on Sunday June 26.

Brexit: What to expect in the first 100 days

In the aftermath of a Brexit result, Britain would start lengthy talks to renegotiate EU agreements and build new trade links with Europe and the rest of the world.

There are concerns these negotiations could be made more difficult because EU bosses would want to discourage other countries from following suit by also leaving the EU.

As well as facing tough talks over Britain's place in Europe and the rest of the world, the country could also face the prospect of another Scottish referendum.

Former First Minister and SNP leader Alex Salmond said, "Should Brexit succeed, Cameron would embark on a two-year negotiated exit, creating a time frame for a new referendum on Scottish independence."

Anti-EU populist parties would seek to ride on the momentum from Brexit ahead of key elections in France, the Netherlands and Germany in 2017.

If Mr. Cameron does step down after the EU referendum, bookmakers have ranked Eurosceptic Tory MP Boris Johnson as the favorite for the next Conservative leader.

Tuesday June 28 and Wednesday June 29: EU summit

If Britain leaves the EU, it could use Article 50 at this summit - triggering the two-year process of the UK's divorce from the EU.

But the country may decide to play for time and delay using the Article 50 legal mechanism as stated in the Lisbon Treaty.

This process has never been used before.

2018 and 2019 onwards: Time to leave the EU?

If the country votes for a Brexit, Britain can withdraw from the EU two years after telling the European Council that its wants to go.

But there would still be lengthy negotiations on the UK's relationship with Europe and it's the trade agreements.

Former Cabinet Secretary Lord O'Donnell warned that the process of breaking ties with Brussels could "take a very long time".

(Compiled by Wang Mingjie, source, The Electoral Commission, The Week Magazine, The Electoral Commission, The Telegraph, The Express)