In every Colorado county, there's a bipartisan group that checks every signature on every ballot and compares it against the most recent official signature on file with that voter. If the group agrees the signatures look different, they'll reject your ballot.
The Secretary of State's Office said this only happens to about 1 percent of voters, but Antonio Chavez in Longmont was one of them.
"So I went Thursday night to check the status of my ballot and it said it was rejected. which has never happened to me before," Chavez said.
The 32-year-old said his signature has changed a lot over the years, but because he renews his license online, his 18-year-old signature is still the one on his license. He never thought that would cause problems with his ballot.
In 2016 the Colorado Secretary of State's office said about 22,000 ballots were initially rejected because signatures didn't match, and 16,209 of them were rejected completely because the voters never followed up to fix the discrepancy.
If rejected, you'll get a notification in the mail, and you have 8 days after the election to fix or "cure" it as the Secretary of State's office calls it.
"If you don't fix it then yes, your ballot's not going to count," said Suzanne Staiert, Deputy Secretary of State.
Chavez is taking time off work Monday to bring a copy of his license to the elections office, but he worries about the others who won't do that.
“I think regardless of where you fall on the political spectrum, this midterm election is considered to be on the most important at least in my lifetime," said Chavez. "And I think you have a lot of new people this election, and if something like this happens to them just think about how disheartening this is."
Chavez only found out his ballot was rejected because he checked the status online. He wishes there was a faster way to notify voters, but Staiert says they don't have access to voter phone numbers or emails.
You can check the status of a mail-in ballot here.