Policy | Center for Election Integrity

ISSUE BRIEF: Requiring Voter Identification For Mail-In Ballots

Anna Pingel,  September 29, 2023

Key Takeaways

Requiring voter identification (voter ID) to verify a mail-in ballot ensures the voter is who they claim to be.

Signature matching is an unreliable and outdated method of verifying a voter’s identity and should be replaced with requiring the last four digits of the voter’s Social Security number, their driver’s license number, or their state-issued voter ID card number.

Both sides of the political aisle have valid concerns about signature matching, and requiring voter ID to cast a mail-in ballot is a solution both parties can embrace.


The quantity of mail-in ballots used in elections has risen in the past decade. According to the U.S. Census Bureau and the Election Assistance Commission (U.S. Census Bureau, 2022; Election Assistance Commission, n.d.), numbers have escalated from approximately 17 million mail-in ballots cast in 2010 (about 19%) to more than 38 million mail-in ballots cast in 2022 (about 34%). Even though the pandemic did lead to a dramatic spike of mail-in ballots, with more than 70 million people voting by mail in 2020, there was already a clearly established upward trend for both midterms and general elections. The increase in use of mail-in ballots is not likely to diminish from the 2022 level, as states have enacted mass mail-in ballot voting and no-excuse absentee ballot requests, and often have codified pandemic-era temporary regulations as law.

Given the proliferation of mail-in ballot voting, it is crucial to protect each vote and each voter by ensuring that a mail-in ballot is cast by the actual person whose name is on it. If the identity of a voter cannot be verified in person, then a functional mechanism of proving identity must be included with the ballot.

Some states require only an unverified signature on a mail-in ballot for it to be counted. Other states require that signature to match the signature on the voter file. However, there are concerns with the process and implications of signature verification. A better alternative is to require voter ID for mail-in ballots. Only five states (Arkansas, Georgia, Ohio, Minnesota, and Montana) have taken the step to truly verify the identity of the voter casting the mail-in ballot, by requiring either the last four digits of the voter’s Social Security number, the voter’s driver’s license number, or the number on the voter’s state-issued voter ID card (National Conference of State Legislatures, 2022). In the state of Georgia, where this requirement was implemented in 2021, requiring voter ID for mail-in ballots did not result in voter turnout reduction in the 2022 election after the law was implemented. Instead, it proved a positive measure for increasing election integrity while not having negative effects on turnout (Georgia Secretary of State, 2022). These options ensure that the voter’s identity is verified and protected when casting a mail-in ballot.

Process for Signature Verification

Election workers may receive training on how to match signatures if their state requires signature matching. It is a process of comparing the lines, curls, and jots that comprise an individual signature. Election workers look for common characteristics in the signature and the voter file, evaluating slant, size and proportion of letters, shape of letters, ending strokes, speed of writing, and pen lifts. Training for election workers can be very limited, and it often varies greatly state by state. This poses a potential issue of poll workers not being properly and uniformly equipped to objectively decide whether a signature belongs to the actual voter.

Another method of verifying a signature is by using software that is programmed to recognize signature characteristics and intended to replace in-person comparisons. However, some of the same concerns—reliability of comparison, differences in signatures over a person’s lifetime, and certain demographics disadvantaged by the programming (Wiggers, 2020)—arise when this method is used. The Election Assistance Commission has weighed in on such software programs by recommending only using automated signature verification software to identify near-perfect matches. It also urges using a sample to double check these results.

Issues with Signature Verification

The political Left and the political Right have identified problems with signature verification, but they focus on different aspects of why signature verification could create issues. The Left emphasizes that signature verification can disenfranchise voters by resulting in improper discarding of ballots. Meanwhile, the Right points out that signature matching opens the door for fraud because it is simple to forge a signature and because signature verification is a subjective process.

It is true that valid ballots have been improperly discarded due to signature verification complications. Aseem Mulji, a legal fellow at the Campaign Legal Center, notes that “[s]ignature evaluation is notoriously unreliable and error prone. It can result in ballot rejections based on nothing more than poor penmanship” (Mulji, 2020). The claim is that signatures change over time, and that groups such as young people, disabled people, and the economically disadvantaged are less likely to maintain a consistent signature (O’Connor, 2018). On this basis, multiple lawsuits have been filed in multiple states that require signature verification.

However, as the Right points out, accepting ballots with signature mismatch problems, or even allowing signature verification to be the only identifying factor on a ballot, opens the door for fraud. The same judge who ruled that there must be a 12-day ballot cure period in the Florida 2018 Senate election rejected the request to count all ballots even if there was a signature mismatch.

Concerns about the process of signature verification itself have also been raised. In April 2022, the Arizona Attorney General published a report detailing concerns about a certain county’s signature verification methods in 2020. The report stated that the “early ballot signature verification system…is insufficient to guard against abuse. At times election workers conducting the verification process had only seconds to review a signature…thus leaving the system vulnerable to error, fraud, and oversight” (Arizona Attorney General Report, 2022).

Finally, multiple experts support that simple signature verification can be an easy avenue for fraud. Faking a signature of a family member, an acquaintance, or a colleague is not difficult. In states with no signature verification requirements, or in states that automatically mail out ballots to the entire voter roll, it is even easier to commit fraud this way. James Green, a forensic document examiner, notes that among other items, election documents are “especially vulnerable to fraud” (Green, 2022). Dr. Linton A. Mohammed, a forensic document examiner, testified before a New Hampshire court that effective signature comparison requires 10 signature samples “at a minimum” to account for variability (Stern, 2018). Signature requirements are not enough to truly and completely protect the voter’s identity.

The Best Alternative: Voter ID Requirements

Requiring voter ID for mail-in ballots instead of signature verification can provide several benefits to ensure the integrity of the voting process. First, voter ID can provide a higher level of objectivity compared to signature verification. With voter ID, a physical document exists that can be checked and verified, which is harder to forge or duplicate than a signature. This requirement can provide a stronger safeguard against voter fraud by ensuring that only eligible voters are casting their ballots.

Second, voter ID can increase confidence in the election process. By ensuring that only eligible voters can cast their ballots, voter ID can help reduce the perception of voter fraud and increase public trust in the electoral process. According to a July 2023 Rasmussen poll, 78% of voters favor requiring the voter to provide their driver’s license number or the last four digits of their Social Security number. The poll also shows that more than half of voters believe that enacting this measure would significantly reduce election fraud.

Finally, implementing voter ID can help ensure consistency in the voting process. Currently, different states have varying requirements for signature verification, which can lead to confusion and inconsistencies in the election process. Voter ID can provide a standard requirement across all states that adopt it, therefore making the voting process more uniform and reliable.

Policy Recommendations

Policymakers should consider the following two measures at the state level.

  1. For all mail-in or absentee ballots cast, require that the voter enter either his driver’s license number, his state-issued voter ID card number, or the last four digits of his Social Security number. The appropriate entity should issue a separate form to be enclosed with the ballot for the purpose of entering this data.
  2. Issue free voter photo ID cards. The appropriate entity within the state should issue free voter photo ID cards to registered voters. These cards should be used only for the purpose of verifying identity to vote, either in person or by entering the identifying number on the appropriate envelope that accompanies a mail-in ballot or absentee ballot. The availability of these cards should also be publicly advertised on the website of the issuing entity.

These two measures will protect and ensure the identity of the voter while removing possible barriers to access of identification. The wait times created by “curing” ballots with mismatched signatures will also be eliminated if identification is required on the front end, which results in earlier election results, certification, and better confidence in election processes. In the 2018 Florida Senate Race, this issue became clear when thousands of ballots were set aside due to signature mismatches. The individuals whose ballots were set aside were then given a period of 12 days to “cure” their ballots by providing identification (Schweers, 2018). Some of these ballots were cured by the voter providing identification (proving that they were in fact who they claimed to be), while many of the ballots were never cured. This issue could have been resolved easily if voter ID had been required in the first place. Doing so would have helped the election reach a final result more quickly.

When these two measures are implemented, it is also important to enact certain privacy and security standards to ensure the voters’ personal information is not stolen. One good way to accomplish this goal is by issuing three envelopes. The first envelope (the smallest one) should contain the ballot for the voter to complete. The second envelope should contain a paper card with the appropriate spaces for the voter ID information. And the third envelope should be big enough to fit both of the other envelopes inside of it and then mailed back as one packet to the election office.


Signature verification is not a reliable system of verifying the identity of the voter.  Instead, states should implement better identification requirements that help ensure that legal votes are in fact counted while also ensuring that signatures are not being forged. Requiring voter identification is an area of opportunity for bipartisan reform. Both political parties can come together to change an outdated practice and move away from extended cure periods, lawsuits, and subjectivity. Requiring voter ID for mail-in ballots is an excellent way to protect voters, and helps make it easy to vote, and hard to cheat.


Anna Pingel is the Policy Analyst for the Center for Election Integrity at the America First Policy Institute.

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