The micro-blogging platform put a warning label in the post and a subsequent tweet, after the politician made a claim without providing any tangible evidence.
The tweets read: "There is NO WAY (ZERO!) that Mail-In Ballots will be anything less than substantially fraudulent. Mail boxes will be robbed, ballots will be forged & even illegally printed out & fraudulently signed. The Governor of California is sending Ballots to millions of people, anyone.....
"....living in the state, no matter who they are or how they got there, will get one. That will be followed up with professionals telling all of these people, many of whom have never even thought of voting before, how, and for whom, to vote. This will be a Rigged Election. No way! (sic)"
The tweets were both accompanied by a warning label in the post.
In response, Trump accused Twitter of "stifling" free speech.
He wrote: ". @Twitter is now interfering in the 2020 Presidential Election. They are saying my statement on Mail-In Ballots, which will lead to massive corruption and fraud, is incorrect, based on fact-checking by Fake News CNN and the Amazon Washington Post....
"....Twitter is completely stifling FREE SPEECH, and I, as President, will not allow it to happen! (sic)"
But now, the site's CEO has explained why they did it and will continue to point out misinformation.
In a series of Tweets, he stated: "Fact check: there is someone ultimately accountable for our actions as a company, and that's me. "Please leave our employees out of this.
"We'll continue to point out incorrect or disputed information about elections globally. And we will admit to and own any mistakes we make ... This does not make us an "arbiter of truth." Our intention is to connect the dots of conflicting statements and show the information in dispute so people can judge for themselves. More transparency from us is critical so folks can clearly see the why behind our actions ... Per our Civic Integrity policy (https://help.twitter.com/en/rules-and-policies/election-integrity-policy ...), the tweets yesterday may mislead people into thinking they don't need to register to get a ballot (only registered voters receive ballots). We're updating the link on @realDonaldTrump's tweet to make this more clear. (sic)"
Trump has vowed to stop tech firms from destroying freedom of speech.
He has since tweeted: "Big Tech is doing everything in their very considerable power to CENSOR in advance of the 2020 Election. If that happens, we no longer have our freedom. I will never let it happen! They tried hard in 2016, and lost. Now they are going absolutely CRAZY. Stay Tuned!!!