Aside from the sheer volume of major life events affecting voter registrations, the challenge is amplified by the simple fact that individuals do not provide updates to their local election offices when any of these life events happen. Election officials rely on systematic list maintenance practices established through state and federal law to update rolls accordingly. Up-to-date and accurate voter registration lists are essential to help ensure only eligible voters can cast a ballot, reduce errors and costs for election officials, and make the process smoother for voters. While data comparison within a state through motor vehicles, vital records, and the courts and corrections system helps election officials maintain registration records in-state, the challenge is more difficult across state lines.
After the passage of the Help America Vote Act (HAVA) in 2002, states began trying to meet this challenge by sharing data with one another in an effort to compare and match voter records and other information. This approach has evolved and taken a number of forms over the past two decades; this explainer will provide a brief history of these interstate matching efforts and describe where these efforts stand now.
This explainer was last updated on October 29, 2025.
Interstate data matching: Goals and challenges
The goal of sharing voter registration (and in some cases other) data across state lines is straightforward. If done successfully, it allows participating states to identify individuals who are simultaneously registered to vote in multiple states, usually because they have moved, and then follow state and federal law to begin the process of removing voters from the rolls where they no longer live. This kind of system can also help prevent the rare instances of people intentionally voting in more than one state.
However, there are several challenges to any cross-state matching process
- What is the quality of the data being shared? Are the data accurate in the first place?
- How is the data kept secure as it is shared between states?
- What data are used to match records? How is that matching done? At what point do the states consider a match to be correct?
This final point may be the most significant challenge of all. Poor or inaccurate matching can lead to false positives, where the matching process incorrectly identifies two records as the same person, when in fact those records pertain to two different individuals. Poor matching can also produce false negatives, where the matching process fails to identify records in different states that actually belong to the same person.
Over the years, a number of states have implemented different approaches to interstate data matching, and have had varying levels of success dealing with these challenges.
Programs of note: 2005-2025
Interstate Crosscheck Program
The first program attempting to identify duplicate voter records across state lines was the Interstate Crosscheck Program. Led by the Kansas Secretary of State’s office, the program started in 2005 with four states (Kansas, Iowa, Missouri, and Nebraska), which all signed a memorandum of understanding (MOU) to share voter registration data.
In this early iteration, this program was hosted by the information technology department of the Iowa Secretary of State’s office, and was described as “a manual process” that used SQL queries to identify matches between corresponding fields. The data shared by states included voters’ first, middle, and last names, their date of birth, a number used to identify voters, county name, and date of registration. Of these, the program used voters’ first name, middle name, last name, and date of birth to match records between states. Records were considered a potential match when all four of these fields matched exactly.
Following some initial testing, the program expanded over the next decade to include nearly 30 states. In 2017, however, public records requests showed that the files were hosted on an insecure server, usernames and passwords were shared by email, and passwords were overly simplistic and changed irregularly. The names, dates of birth, and partial Social Security numbers of 945 voters were made public; the U.S. Department of Homeland Security subsequently conducted an audit of the program’s security practices. Following a lawsuit related to these issues, the program was suspended in 2019 and has been dormant since then.
Kentucky, South Carolina, and Tennessee
In 2006, Kentucky, South Carolina, and Tennessee began a pilot project to share data and compare lists of registered voters. Since voter registration records in all three states included full Social Security numbers, officials were hopeful this would increase the accuracy of their data matching to identify voters who were registered in more than one state. To implement the project, Kentucky and Tennessee sent voter records to South Carolina, where the state election office used a computer program to compare and match data between the three states.
In April 2006, the Kentucky Secretary of State's office, “using the information provided by South Carolina, had identified those people on the voter rolls who were registered more recently in either South Carolina or Tennessee.” As a result, the state removed 2,110 Kentucky voters who were also registered in South Carolina, and 5,995 voters who were registered in both Kentucky and Tennessee.
A month later, the state held a primary election. According to litigation related to the program, 259 of those who had been removed from the rolls showed up to vote, representing a 10 percent error rate in the matching process. A court decision ultimately ordered that all voters who had been removed from the rolls in Kentucky be put back on. In the decision, the court also noted that it had detected no malicious or partisan intent behind the removal of voters, calling cross-state data matching an “innovative” tool but stipulating it required improvement before being put into use.
Louisiana
In 2007, Louisiana’s Secretary of State led a matching process with several other states (Colorado, Florida, Georgia, Tennessee, and Texas) as well as the counties/cities of Las Vegas, New York, and San Diego. The process conducted by the state sought to identify exact matches of a voter’s last name, first name, and date of birth; it also looked at the last date of registration, identifying which jurisdiction had seen the most recent registration activity. Letters were sent to thousands of registered voters who returned a positive match, informing them that the state had identified them as registered in another state and requiring them to take action to avoid being removed from the rolls.
During the matching process, the Secretary of State’s office noted some challenges. The state attempted to address some of these challenges in its communications with local registrars, which were voters’ main points of contact. The Secretary of State’s office recommended that if a voter called with questions about the letter they had received, the registrars could ask for identifying information, such as mother's maiden name or last 4 digits of the Social Security number, to make a better determination for a match.” The secretary’s office also requested that registrars double-check the list of voters in their jurisdiction that had been flagged as having a possible match in another state, as they were “concerned that some possible matches may not contact us and ultimately get canceled when they should not be canceled” and wanted to ensure the state was erring “on the side of the voter.”
As in Kentucky, there was a legal challenge to this process, and some voters who were removed from the rolls were later restored.
Oregon and Washington
In 2008, Oregon and Washington worked with academics and other experts to conduct a pilot project that matched their voter registration databases. The pilot used two types of matches. The first required matching voters’ complete first name, complete middle name, complete last name, and date of birth. The second used the complete first name, the first character from the middle name field, complete last name, and the date of birth. The matching process was done by staff from the Oregon Secretary of State’s office using FileMaker Pro.
In total, 5,461,040 records were run through the matching process. Using both matching types, the states found 8,292 matches, corresponding to a match rate of 0.152%. The first matching process (which included voters’ full middle names) identified 3,482 matches; the second match type (which used only the middle initial) found an additional 4,810 matches.
The states followed up with a subset of these matches, focusing on 1,312 voters in counties along the border of both states; the states also checked when and where these voters’ most recent voter registration activity was. These voters received a mailing asking whether they wanted to cancel their registration in the state where they no longer lived. Based on the responses they received, Oregon removed 379 voters from its rolls, and Washington removed 352. If the states received no response from an individual who was sent the mailing, they made no changes to the voter record.
Electronic Registration Information Center
The Electronic Registration Information Center (ERIC), founded in 2012, is a nonprofit, nonpartisan organization created to help U.S. states improve and maintain the accuracy of their voter lists, as well as improve access to voter registration for individuals who were eligible to vote but had not yet registered.
The organization was officially formed with support from seven founding states: Colorado, Delaware, Maryland, Nevada, Utah, Virginia, and Washington. As of May 2025, it comprises 24 U.S. states and the District of Columbia, totaling 25 member jurisdictions. This marks a decline from the peak of ERIC membership in 2022, when 33 states and states and the District of Columbia were members; since then, Louisiana, Alabama, Florida, Missouri, West Virginia, Iowa, Ohio, Virginia, and Texas have left the organization.
While the original idea was developed through research and conversations led by the Pew Charitable Trusts, ERIC is directed and funded by its member states. New members pay a one-time membership fee as well as annual dues, which are based in part on the size of the citizen voting-age population in each state. Once a member joins, they submit their voter registration data and data from their motor vehicle departments (MVDs) at least every 60 days. Once they receive members’ data, ERIC staff use “data matching software to compare data from all member states, sometimes with data from other sources, to create list maintenance reports.”
The process generates four core reports for member states. The “Cross-State Movers Report” uses both voter registration data and MVD data to identify voters who appear to have moved from one member state to another. The “In-State Movers Report” uses the same data to highlight voters who appear to have moved within a member state. Using only voter registration data, ERIC provides a “Duplicate Report,” identifying voters with duplicate registrations within the same state. The final core report, the “Deceased Report,” pulls on voter registration data as well as death data from the Social Security Administration to identify voters who have passed away.
In addition to these core reports, ERIC also offers three additional reports to member states. These additional reports pull on member data and federal data sources to identify: 1) individuals who appear to be eligible to vote but are not yet registered, 2) voters who have moved and changed their address with the US Postal Service, and 3) potential illegal voting activity. This last report, the “Voter Participation Report,” provides information on “voters who may have cast ballots in more than one state, more than one ballot in the same state, or who may have voted on behalf of a deceased voter.”
Members use these reports to support their list maintenance processes, provide voter registration information to unregistered individuals, and review any possible cases of illegal voting. As of April 30, 2025, ERIC had identified 13,513,637 cross-state movers since 2013. The organization provides a public record of the inaccurate or out-of-date records it has identified for its member states on its website: https://ericstates.org/statistics/.
Alabama Voter Integrity Database
The Alabama Voter Integrity Database (AVID) was started in 2023 by the Alabama Secretary of State’s office. In addition to Alabama, nine states—Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, Ohio, Texas, and Tennessee—have signed on to participate in the program by establishing memoranda of understanding (MOUs) between each partner state and Alabama.
According to the most recent MOU from April 2025 establishing a partnership between Alabama and Ohio, the scope of the program is as follows:
- “Each Party will share its voter file containing statewide voter registration data to the other participating Party in a format and on a schedule to be determined by mutual agreement executed by the Parties in writing.
- All data will be transferred to and from the participating Parties using industry standard encryption technology and passwords as determined by mutual agreement in writing executed by the Parties.
- Each participating Party's voter file containing voter registration data will be compared to the voter file containing voter registration data from the other participating Party.
- Each Party will return the results of the data matching to the other participating Party in a format and on a schedule to be determined by mutual agreement executed by the Parties in writing.
- Each participating Party shall maintain procedures and controls pursuant to their respective state laws for the purpose of assuring that information in its possession is not mishandled, misused, released, disclosed, or used in an inappropriate manner by it, its agents, officers, or employees. All Parties to this Agreement shall take all reasonable steps and precautions to safeguard this information. All Parties to this Agreement shall produce the information subject to their respective state's public records laws.”
Because the program is still relatively new, there is limited information on the details of the matching process or specific data and results.
Conclusion
Keeping up with voters, especially as they move from one state to another, continues to be a significant issue for election officials. Cross-state data matching is one approach that can help identify these movers, one that states have been trying different approaches to for twenty years. While they have encountered several challenges inherent in the matching process, officials in many states have found that, when done well, it can help them maintain more accurate voter lists.