Why some campaigners urge people to spoil their ballots - instead of not voting
Politicians have been courting voters for weeks - but some of those casting a ballot on Thursday won't be backing any candidate.
At the last general election, more than 100,000 people spoilt their ballot papers - in a wide variety of ways.
But why do people go to the effort of visiting a polling station or filling out a postal vote if they don't want to back a politician?
Sky News looks at why and how people spoil their votes - and what happens next.
Why do some voters spoil their ballot papers?
It is thought many people who cast invalid votes do so deliberately because they simply do not like any of the candidates or parties on offer.
Some voters might support a party that is not standing in their area, or they may be undecided over who to back.
Over 18s in the UK can only cast one vote for one candidate - but more than 20,000 people backed at least two in the last general election.
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Why are dissatisfied voters encouraged to spoil their ballot?
People who are fed up with politicians generally - or the particular ones standing in an election - have the easy option of simply not turning up on voting day or shunning the option of a postal vote.
At the last general election, in 2019, the turnout across the UK was 67.3% - meaning millions of adults did not vote.
However, campaigners argue it is better to show up and spoil your ballot paper than stay away, even if you don't like any of the candidates.
Voting Counts, an organisation that aims to improve political engagement among young adults, says it is a good way for someone to demonstrate their dissatisfaction with politicians.
By spoiling your vote "you become a voice for the disengaged", it argues.
The group notes that, because all spoilt votes are counted and recorded, "your apathy towards the political parties will be heard not just forgotten".
The hope is if there are lots of blank or spoilt votes, it puts pressure on politicians to think about how to reconnect with disengaged voters.
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How do people spoil their votes?
When it comes to casting an invalid vote, the ballot paper is your canvas - campaigners argue.
One common technique, as mentioned above, is to back more than one candidate, while others leave their voting paper blank before popping it in the ballot box.
Some might write an X in every box - or daub a giant one across the whole ballot paper.
But some get more creative with expletives, rants about politicians or drawings - of all kinds of things...
A penis can still count - if it's drawn carefully
In the 2015 general election, Conservative MP Glyn Davies was awarded a vote he wasn't necessarily counting on when a rude image drawn next to his name was determined to be a valid vote.
Mr Davies wrote on his Facebook page at the time: "One voter decided to draw a detailed representation of a penis instead of a cross in my box on one ballot paper.
"Amazingly, because it was neatly drawn within the confines of the box the returning officer deemed it a valid vote.
"I'm not sure the artist meant it to count, but I am grateful. If I knew who it was, I would like to thank him (or her) personally."
What happens to spoilt votes?
When a vote counter comes across a ballot paper that has been scrawled on or otherwise defaced, it isn't immediately declared spoilt.
First, it is put in a pile of "doubtful" ballot papers.
Blank votes, clearly spoilt ones, and ones where the counter is not sure of the voter's intention, all go in this pile.
The returning officer - the person in charge of the count - will then go through them to determine which ballots are invalid.
The Electoral Commission says they do not need to wait until the end of the count to do this, and advise that the process "should be carried out regularly throughout the count in clear view of those entitled to be present".
If a voter's intention is unclear, if they have left their ballot blank, if they have broken the rules (such as voting for more than one candidate) or if they have clearly spoilt the paper, then a ballot will usually be declared invalid.
However, counting agents, who are at the counting venue on behalf of candidates, can object if they think the vote should be counted.
At the end of the count, the number of spoilt votes is tallied and announced along with the number of votes each candidate has won.
How many people spoil their ballots?
In the last UK general election in 2019, 0.36% of votes were rejected - a total of 117,101 ballot papers.
These included 20,983 ballot papers where the voter marked more than one candidate, 1,585 which included an "identifying mark" and 93,959 that were "unmarked".
Chorley in Lancashire had 1,303 invalid votes - the largest number out of any constituency in the UK and the equivalent of one in every 31 valid votes cast in the region.
However, the seat was home to Speaker of the House Sir Lindsay Hoyle - and so by tradition the Conservatives, Labour and the Liberal Democrats did not field a candidate there.
The total number of spoilt ballots in 2019 represented a 58% increase on the 74,189 votes that were rejected at the 2017 general election.
