People living in the Greater Manchester constituency of Makerfield are heading to the polls to elect their new MP.
More than 30 polling stations across the parliamentary constituency opened at 07:00 BST and will close at 22:00, after which the count will take place. The result is expected early on Friday.
There are 14 candidates standing in the by-election, which was triggered by the resignation of Labour MP Josh Simons.
It is one of three Westminster by-elections taking place, with voters in the Scottish constituencies of Arbroath and Broughty Ferry and Aberdeen South also heading to the polls after their MPs stood down to take up posts as MSPs following May's Holyrood elections.
Voters have been reminded to bring a valid form of identification with them.
A passport, driving licence, bus pass, blue badge and a voter authority certificate are all accepted.
Photo IDs that are out of date can still be used if the image still looks like you.
Photocopies are not permitted.
The full list of candidates for the Makerfield by-election (in alphabetical order by surname) are:
Jake Austin, Liberal Democrats
Count Binface, Count Binface Party
Andy Burnham, Labour and Co-operative Party
Dan Clarke, Libertarian Party
John Dyer, Independent
Ed Gemmell, Climate Party
Paul Gould, Independent
Alan 'Howlin' Laud Hope, The Official Monster Raving Loony Party
Robert Kenyon, Reform UK
Robert Pownall, Independent
Rebecca Shepherd, Restore Britain
Sarah Wakefield, Green Party
Peter Ward, Rejoin EU
Michael Winstanley, Conservative Party
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