EXIT poll results give an indication of what the final outcome of an election could be.
But how do they work? We explain it all.
Brits head down to their local polling booth for general and local elections
What is an exit poll?
They are surveys of a small proportion of voters leaving polling stations across the UK.
Researchers ask which party the individual voted for, as well as their age, race and gender.
The form is completed anonymously and placed in a ballot box.
It is primarily used to calculate turnout and electoral swing – the extent of change in voter support compared to the previous election.
Data can’t be released before the polls have closed.
Are they accurate?
Due to only a small sample of voters filling out questionnaires, those doing so are likely to be younger, so this may skewer results.
Also, voters head to the polls at different times so a single exit poll may not give a true reflection of the overall outlook of the national vote.
However, pollsters tend to return to the same polling stations at the same times at each election.
And by comparing these results it is possible to work out how voting has changed in that particular constituency.
Have there been any issues?
A famous example of an election poll error happened in 1992.
Two exit polls predicted a hung parliament – but the actual vote revealed the Tory government under John Major held their position.
Investigations later revealed a number of causes including the shy Tory factor and inadequate demographic data.