While Americans have voted by mail in many election cycles, the number of people who voted by mail in 2020 was unprecedented because of the coronavirus pandemic.

To avoid the crowds at polling locations on election day, more than 100 million Americans cast early or absentee votes, doubling the total who did so in 2016.

President Trump has described mail-in voting as “the scam of all time”, claiming that it allows widespread voter fraud. It does not, say the experts. But is there any evidence to back up his claims?

Sky News’ team in the US, Alistair Bunkall, James Matthews and Becky Cotterill, have examined Trump’s most popularised election theories to see if there is any truth to them.

Is voter fraud widespread among mail-in voting?

Top officials at the Department of Homeland Security issued a statement declaring the 2020 election “the most secure in American history”.

“There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised.”

Were ballots that arrived late counted?

The Trump campaign has claimed that ballots arriving after election day were illegally counted.

However, 22 states and Washington DC allowed ballots to arrive after the 3 November if they were postmarked by election day.

There is no evidence that states counted ballots that arrived after their deadlines.

Did military ballots go missing in Georgia?

Three days after the election President Trump tweeted: “Where are the missing military ballots in Georgia? What happened to them?”

At the time of Trump’s tweet, Georgia was still waiting to receive 8,410 military ballots by mail.

These ballots were not missing. The deadline for receiving those ballots had not yet passed at the time of Trump’s tweet. In fact the ballots had just over four hours to arrive to be counted by the state’s deadline (5pm on 6 November).

“There are ballots that are going to make it, there are ballots that are not going to make it,” said a Georgia election official. “We are going to count all the legal ballots.”

Were late ballots backdated in an attempt to allow them to be counted?

A postal worker in Pennsylvania claimed that managers instructed workers to backdate ballots mailed after election day, so that they could be included in the count.

This prompted senior Republican senator Lindsey Graham to write to the Justice Department demanding an investigation. The following day attorney general William Barr authorised federal prosecutors to look into allegations of voter fraud.

However the postal worker who made the initial claims has subsequently confessed they aren’t true and signed an affidavit recanting his allegations.

Did a “software glitch” cause ballots to switch from Trump to Biden in Michigan?

A clerk in Michigan forgot to update software on the ballot counting machine meaning that thousands of votes went to Joe Biden when they should have been recorded for Donald Trump.

Systems in place caught the error before it went further and it was quickly corrected.

So this allegation is true, in a sense, although the error was human not software-related and the final result was accurate.

Republican clerks have also vehemently dismissed the claims of fraud as “categorically false”.

Were the identities of four deceased people used to vote in Georgia?

Two of these allegations have been proven false.

Officials in Georgia found that one of accused was actually removed from the voter rolls when they died in 2003 – a person with a similar name voted legally this year though, which is maybe where the confusion arose.

A second was also removed from the voter roll after his death so didn’t vote in 2020 – his wife however did vote, using his name but the ‘Mrs’ prefix. Again, this has been cleared up.

Officials are still looking into the other two allegations.

Donald Trump tweeted: “THE OBSERVERS WERE NOT ALLOWED INTO THE COUNTING ROOMS.” Were they?

There’s no evidence of this. Indeed, the Republican lawyers who have brought legal challenges – in Pennsylvania and Nevada – have acknowledged that observers were given access.

The legal action has centred not on the denial of access, but on how close observers could get to the count.

Wisconsin voter numbers – a fraud?

“Looks like fraud!” tweeted Eric Trump, Donald’s son, in response to incorrect social media claims about voter turnout in Wisconsin.

An image suggested there had been 3,170,206 votes counted but only 3,129,000 registered voters, adding “WISCONSIN REPORTING 101+% VOTER TURNOUT!”

In fact, the Wisconsin Elections Commission had 3,684,726 registered voters in the days before election day.

Is the #Sharpiegate conspiracy theory true?

Trump allies have promoted the so-called #Sharpiegate conspiracy. This relates to the felt-tip ‘Sharpie’ pen given to voters to mark their ballot paper.

Trump supporters fuelled doubt over the Arizona count by promoting the theory that vote-scanning machines in Maricopa County, Arizona, couldn’t read ballots marked by the Sharpie.

Arizona election officials have repeatedly insisted that its machinery is fully compatible with the use of the Sharpie pen and that there is no truth in any suggestion otherwise.

By way of explanation, Maricopa County Elections Department tweeted: “Transparency and security is of the utmost importance to us. We provided Sharpies to be used for in person voters at all Maricopa County Vote Centers.

“After multiple tests, we found Sharpie to have the fastest-drying ink and best suited for our Vote Center tabulators.”