Mail Ballot Voter Identification

In Colorado, 92 percent of voters cast their ballots by mail in 2024, and those ballots are currently verified by matching the voter's signature on the envelope to the state database.

Every active registered voter in Colorado automatically receives a ballot by mail. According to the 2026 State Ballot Information Booklet, 92 percent of all ballots cast in 2024 were mail ballots.

When a voter returns a mail ballot today, they must sign the outside of the return envelope. Election staff and bipartisan election judges compare this signature to the voter's signature on file, such as from their driver's license or past voter records. If the signature is missing or does not match, the county contacts the voter. The voter then has eight days after Election Day to "cure," or fix, the issue so their ballot can be counted.

Measure A84 would require voters to also write an identification number, such as the last four digits of a Social Security number or Colorado driver's license, on the envelope. Supporters say an ID number provides an objective verification method that promotes public confidence in elections. Opponents say the current signature verification process is already secure, and argue that requiring an ID number on the envelope raises privacy concerns and could cause valid ballots to be rejected.

Several states require an ID number or a copy of a photo ID with a mail ballot, with varying impacts on voter participation.

According to the National Conference of State Legislatures and Ballotpedia, while most states rely on signature matching, some require additional identification: * Texas and Georgia require an ID number, like a driver's license or partial Social Security number, on the ballot envelope. * Arkansas and North Carolina require a physical copy of a photo ID returned with the ballot. * Alabama, Kentucky, and New Hampshire require a copy of an ID when requesting a mail ballot.

When Texas added its ID number requirement in 2021, mail ballot rejections spiked. A 2025 Brennan Center study found that of 18,000 Texas voters whose mail ballots were rejected in the 2022 primary, only 344 voted in person, lowering turnout for that group. Conversely, when Georgia added a similar requirement in 2021, an Atlanta Journal-Constitution analysis found only 0.6 percent of absentee ballots were rejected for ID issues in late 2021 elections.

Supporters, including Georgia's Secretary of State, argue ID requirements add security without reducing access. Opponents, like the group VoteRiders, argue the rules confuse voters and create barriers for those lacking the required documents.

Six other states currently require voters to write an identification number on their mail ballot return envelope.

According to the National Conference of State Legislatures and Ballotpedia in 2026, these states are: * Georgia * Minnesota * New Mexico * Ohio * Texas * Utah (which added the requirement in 2025)

In these states, voters must provide a driver's license number, a state ID number, or the last four digits of their Social Security number on the outside of the envelope. Election officials then compare this number to the voter's registration record.

Currently, Colorado verifies mail ballots by comparing the voter's signature on the envelope to the signature on file. Measure A84 would add the ID number requirement on top of the signature check.

If a voter forgets to include the number or writes a number that does not match their record, the ballot can be rejected. In Texas, a 2021 law requiring ID numbers on ballot envelopes led to rejected ballots when voters could not remember which number they originally used to register, according to 2025 reporting by Votebeat.

The Colorado Legislative Council estimates that checking these identification numbers and notifying voters of errors would cost state and local governments up to $2.7 million in the first year and $1.2 million annually after that.

In recent elections, Colorado has ultimately rejected between roughly 18,000 and 35,000 mail ballots due to missing or mismatched signatures.

• In 2024, 35,255 ballots were rejected for signature mismatches, according to federal Election Administration and Voting Survey data.
• In 2020, 21,838 ballots were rejected for signature verification issues, according to the Colorado Secretary of State's Office.
• In 2016, about 18,800 ballots were rejected for signature issues (roughly 16,200 for discrepancies and 2,660 for missing signatures), according to a Colorado Sun analysis of state data.

These figures represent ballots that remained uncured. Under current law, if a bipartisan team of election judges finds a missing or mismatched signature, the county must notify the voter. Voters have until eight days after Election Day to fix or cure the issue, often using the state's TXT2Cure smartphone system.

Supporters of Measure A84 argue that signature matching is subjective and an ID number provides a more secure, objective way to verify identity. Opponents argue the current signature verification system works well and that adding an ID requirement will cause more eligible voters to have their ballots rejected over simple clerical errors.

There is currently no reliable official figure for exactly how many registered voters in Colorado lack a Social Security number, state driver's license, or state ID.

To register to vote in Colorado, residents are asked to provide a state driver's license, state ID, or the last four digits of their Social Security number. Voters without these can still register but must provide an alternative identification, such as a utility bill or passport, when voting. Because of this, most registered voters already have one of the required numbers on file.

Neither the 2026 State Ballot Information Booklet (the state's official voter guide known as the "Blue Book") nor the measure's fiscal note provides a specific count of voters lacking these IDs.

Supporters of Amendment 84 argue that requiring these numbers adds security to mail ballots, noting that most people already use these IDs for daily activities. Opponents argue the requirement could disenfranchise eligible voters who lack these specific documents. While Colorado-specific data is unavailable, opponents of similar 2026 measures in other states cite a University of Maryland survey estimating that 21 percent of voting-age Americans lack a driver's license with their current name and address.

In states that recently added ID number requirements to mail ballots, rejection rates initially spiked before settling at levels higher than in previous years.

Texas and Georgia both passed laws in 2021 requiring voters to provide a driver's license or Social Security number on their mail ballots.

According to data from the U.S. Election Assistance Commission and state election offices, Texas experienced the most significant changes: * In the 2020 general election, Texas rejected 0.8 percent of mail ballots. * In the 2022 primary, the first election under the new law, the rejection rate jumped to 12.4 percent, with most rejections caused by missing or mismatched ID numbers. * By the 2022 general election, the Texas rejection rate dropped to 3.4 percent, which was still more than four times its 2020 rate and more than double the 2022 national average of 1.5 percent.

Georgia saw a smaller increase, with its mail ballot rejection rate rising from under 1 percent in 2020 to 1.7 percent in the 2024 general election.

Supporters of ID requirements argue they improve election security by replacing subjective signature matching with objective, verifiable data. Opponents argue the requirements cause confusion and disproportionately disenfranchise older voters, voters with disabilities, and those who cannot remember which ID number they originally used to register.