Polls opened at 07:00 BST on Thursday, with counting starting once voting ends at 22:00 BST.
A total of 650 Westminster MPs will be elected, with about 46.9 million people registered to vote.
That is up from the last general election, in 2015, when there were 46.4 million registered voters.
Some votes have already been cast, through postal voting, which accounted for 16.4% of the total electorate at the 2015 general election. People with an undelivered postal vote can still deliver it by hand to their local polling station.
Overall turnout in 2015, when the Conservatives won 331 out of 650 seats, was 66.4%, up from 2010.
Most polling stations are in schools, community centres and parish halls, but pubs, a launderette and a school bus have been used in the past.
Police have increased security at polling stations, including patrols by armed officers in some areas, following the recent terror attacks.
A handful of seats are expected to be declared by midnight, with the final results expected on Friday afternoon.
Unusually, no local elections are taking place at the same time, so results might come through earlier than in recent general elections.
In 2015 the first seat to declare was Houghton and Sunderland South, at 22:48 BST.
To form a majority in the House of Commons one party must win 326 seats – in 2015 a Conservative majority was not confirmed until 13:34 BST.
The weather forecast is for some rain in south-west England, Northern Ireland, Scotland and Wales on Thursday, with south-east England remaining cloudy and dry.
Polls close at 22:00 BST, but officials say anyone in a polling station queue at this time should be able to cast their vote.
The BBC’s main election programme, fronted by David Dimbleby, starts at 21:55 BST, with live coverage from scores of counts.
Dimbleby, fronting his 10th election night broadcast, will be joined by Mishal Husain, Emily Maitlis, Jeremy Vine.
Wales, Scotland and Northern Ireland will have their own overnight programmes but will join Huw Edwards from 07:00 BST on 9 June.
On the radio, an overnight broadcast by BBC Radio 4 will be hosted by Jim Naughtie and Carolyn Quinn.
On BBC Radio 5 live, the overnight show will be hosted by Stephen Nolan and Emma Barnett.
Full coverage of the results as they come in will be on the BBC politics online live page and front page scorecard, with all the big breaking stories from around the country and analysis by correspondents.
A Freelance Journalist, Entrepreneur and Philanthropist. Editor-in-Chief of www.233times.com. A contributory writer for Ghanaian Chronicle Newspaper. An alumnus of Adisadel College where he read General Arts. He holds first degree in Bachelor of Arts from the University of Ghana; Political Science (major) and History (minor). He has also pursued MSc Corporate Social Responsibility (CSR) and Energy with Public Relations (PR) at the Robert Gordon University in the United Kingdom. His mentors are Rupert Murdoch, Warren Buffet, Sam Jonah, Kwaku Sakyi Addo and Piers Morganview all posts by: Nana Kwesi Coomson
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