Exit polls explained: When and what to expect from the UK election

British Prime Minister Theresa May and Labour leader Jeremy Corbyn have already cast their votes with the UK’s general election already well underway.

The Conservatives, May’s party, currently hold a lead ranging one to 12 points.

The difference is between a hung parliament when polls close at 7am AEST and a 100-seat Tory majority.

What is an exit poll?

When voters leave the polling station they fill out a survey asking how they voted.

The poll is designed to give an early indication of how the election will turn out before all the votes are counted.

This can take a few hours, particularly if recounts are needed.

What time is the exit poll?

Australians can expect to see results for an exit poll, conducted by Ipsos MORI, at about 7am AEST.

Can it be trusted?

There is always a margin of error in exit polls and results are sometimes way off.

A 2015 UK exit poll predicted the Conservatives would win 77 more seats than Labour, who were ahead in the opinion polls.

It predicted: Conservative 316, Labour 239, SNP 58, Liberal Democrats 10, others 27.

But the actual result was: Conservative 331, Labour 232, SNP 56, Liberal Democrats 8, others 23.

However, a 2005 exit poll predicted the Conservatives to win 307 seats, which they did.

There are some issues with how exit polls are carried out though, with postal votes not counted.

How many seats are needed for the majority?

The number is 326, but if no party achieves this, a hung parliament is likely.

Australians are most likely to see a result at about 1pm AEST.