Electronic voting in the United States involves several types of machines: touchscreens for voters to mark choices, scanners to read paper ballots, scanners to verify signatures on envelopes of absentee ballots, adjudication machines to allow corrections to improperly filled in items, and web servers to display tallies to the public. Aside from voting, there are also computer systems to maintain voter registrations and display these electoral rolls to polling place staff.
Most election offices handle thousands of ballots, with an average of 17 contests per ballot, so machine-counting can be faster and less expensive than hand-counting.
Voluntary guidelines
The Election Assistance Commission (EAC) is an independent agency of the United States government which developed the 2005 Voluntary Voting System Guidelines (VVSG). These guidelines address some of the security and accessibility needs of elections. The EAC also accredits three test laboratories which manufacturers hire to review their equipment. Based on reports from these laboratories the EAC certifies when voting equipment complies with the voluntary guidelines.
Twelve states require EAC certification for machines used in their states. Seventeen states require testing by an EAC-accredited lab, but not certification. Nine states and DC require testing to federal standards, by any lab. Four other states refer to federal standards but make their own decisions. The remaining eight states do not refer to federal standards.
Certification takes two years, costs a million dollars, and is needed again for any equipment update, so election machines are a difficult market.
A revision to the guidelines, known as the VVSG 1.1, was prepared in 2009 and approved in 2015. Voting machine manufacturers can choose which guidelines they follow. A new version has been written known as the VVSG 2.0 or the VVSG Next Iteration, which is being reviewed.
Optical scan counting
In an optical scan voting system, each voter's choices are marked on one or more pieces of paper, which then go through a scanner. The scanner creates an electronic image of each ballot, interprets it, creates a tally for each candidate, and usually stores the image for later review.
The voter may mark the paper directly, usually in a specific location for each candidate, then mail it or put it in a ballot box.
Or the voter may select choices on an electronic screen, which then prints the chosen names, usually with a bar code or QR code summarizing all choices, on a sheet of paper to put in the scanner. This screen and printer is called an electronic ballot marker (EBM) or ballot marking device (BMD), and voters with disabilities can communicate with it by headphones, large buttons, sip and puff, or paddles, if they cannot interact with the screen or paper directly. Typically the ballot marking device does not store or tally votes. The paper it prints is the official ballot, put into a scanning system which counts the barcodes, or the printed names can be hand-counted, as a check on the machines.
Most voters do not look at the machine-printed paper to ensure it reflects their choices. When there is a mistake, an experiment found that 81% of registered voters do not report errors to poll workers. No state requires central reporting of errors reported by voters, so the occasional report cannot lead to software correction. Hand-marked paper ballots more clearly have been reviewed by voters, but some places allow correction fluid and tape so ballots can be changed later.
Two companies, Hart and Clear Ballot, have scanners which count the printed names, which voters had a chance to check, rather than bar codes and QR codes, which voters are unable to check. When scanners use the bar code or QR code, the candidates are represented in the bar code or QR code as numbers, and the scanner counts those codes, not the names. If a bug or hack makes the numbering system in the ballot marking device different from the numbering system in the scanner, votes will be tallied for the wrong candidates. This numbering mismatch has appeared with direct recording electronic machines (below).
Errors in ballot marking devices Ballot marking devices display contests and candidates on a screen where voters can make, change and check selections before printing the choices on paper to put in a ballot box. The election worker provides a code for each voter, to tell the machine what contests that voter may vote on. Contests presented to voters depend on the district boundaries they live in.
A common concern is picking one candidate and having the machine register another. Staff say that touching the touch screen near a boundary between candidates, or with a tremor can choose the wrong candidate, so voters need to check. If they discover a mistake after printing the ballot, they can spoil that ballot and start over. Some places put a privacy screen over the BMD's display, so voters must be "aggressive" when pressing the touchscreen to register a vote. In a 2023 election in Northampton County, PA, misprogramming switched text on paper between two judge retention contests, so a vote to remove or retain the first was labeled with the name of the second, and vice versa. The county briefly changed to hand-marked paper ballots, but ran out, and went back to the mislabeled BMDs. The county and court changed instructions throughout the day. In a 2022 election in Marietta, GA, up to 157 voters were presented lists of contests which were partly in error, due to recent changes in district boundaries. In a 2019 election in Philadelphia, PA, 40% of polling locations had problems with BMDs, including "touchscreens that were hypersensitive or that froze; paper voting receipts getting jammed in the machines; and panels opening on some machines to expose the equipment's electronic controls." In a 2019 election in Northampton County, PA, BMD screens were hypersensitive or insensitive, from being "configured improperly in the factory" so voters had to keep trying to select their candidates. An instructional message was treated as a Republican candidate, so straight party votes omitted the real candidate.
Errors in optical scans Some scanners have a row of photo-sensors which the paper ballot passes by, and they record light and dark pixels from the ballot. Other scanners work by scanning the ballot to create an electronic image (i.e. a picture) of the ballot. Then the resulting image (picture) is analyzed by internal software to discern what votes were cast. In these types of vote tabulators, any defect in the scanning apparatus, such as dirt, scratches on the lens, or chads of paper, may mar the image of the ballot. These types of defects may produce long black lines, or white lines in the ballot image, which then may be misread by the software as an undervote (no votes for anyone), or as an overvote (a vote for every candidate). Some offices blow compressed air over the scanners after every 200 ballots to remove dust.
Software can miscount or fail to count. If it fails or miscounts drastically enough, people notice and check. Errors can happen in the scanner or at the ballot printer. Staff rarely identify the person who caused an error, and assume it was accidental, not a hack.
2025 In the 2025 general election, Rensselaer County, NY, formatted ballots and computers differently, and corrected with a hand count, so a state forest proposal gained 382 votes, a library levy gained 480 votes, and a rescue squad proposal gained 1,733 votes, changing outcomes for the latter two. The library had collected signatures from more voters for the levy than the computer results showed, and the county found a misprint. Citizen groups asked the state Attorney General to investigate. In the 2025 general election, Cambridge, MA included 2,158 test ballots in its count. When they recalculated without them, one school board result changed.
2024 In the 2024 general election in Sandoval County, NM, the memory device from one precinct became unreadable when a worker mishandled it, totals were inconsistent, and two voting machines were used without seals. Officials certified results anyway, and one candidate filed a complaint. In the 2024 general election in Ashtabula County, OH, scanners mis-counted votes for levies, because the state Supreme Court changed the wording of the first state-wide ballot measure, so other measures shifted from where the scanners expected them on the page. The problem was discovered only when the county hand counted one measure because it was very close. Then the county hand counted other measures. Three measures changed from losing to winning. Other Ohio counties reported some ballots as unreadable, but did not hand count any ballots to check for shifted votes. In the 2024 general election in Torrington, CT, broken tabulators and coding which did not match the layout of the printed ballots caused errors in counts of absentee and early ballots and ballots of voters who registered the same day they voted. Staff recounted these 7,000 ballots by hand. In the 2024 general election in Centre County, PA, results from 13,000 scanned ballots did not upload to the central election computers, and were rescanned. In the 2024 general election in Cambria County, PA, software and printing errors prevented counting votes on election day. Polls stayed open late and ballots were counted later. In the 2024 general election in Nevada and Shasta Counties, CA, bar codes on the edges of ballots which tell machines the "style" or contests on the ballot were imprecisely printed ("ink overspray") by Runbeck, the ballot printing company, so scanners could not read them and process the ballots. They were hand-copied onto better ballots. In the 2024 primary in Shasta County, CA, 100 ballots appear in the scanners' audit logs and not in final results, in a district with a contest decided by 14 votes. The logs show 20 manual time changes in 4 machines, half of which were logged exactly 60 seconds after a previous update. Seven were outside working hours, between nine at night and 4 in the morning, when video surveillance showed no one present. The county asked the US Justice Department to investigate. In a 2024 primary in Utah, "adjudicated ballots were not reflected in the total results" in at least Tooele and Washington Counties, when more than a few adjudicated ballots were entered at once. In a 2024 primary throughout Puerto Rico, parties found over 1,000 errors. The elections commission said the voting machines "incorrectly calculate vote totals". The election commission then "conducted a full vote tally and audited paper receipts from hundreds of ballot-counting machines." Dominion said the errors were in their software which exports counts from the voting system for public release.
2022 In a 2022 election in Alameda County, CA, software was wrongly set to skip 250 ballots in round 1 of Ranked Choice Voting. These ballots had no first choice and should have been counted by their top choice. FairVote saw the error, and the county corrected result, which changed the winner in Oakland Unified School District 4. In a 2022 election in Monmouth County, NJ, software did not notice when staff uploaded six flashdrives of ballot images twice, which added more votes to candidates and switched a school board winner. It was caught by a council member who thought the numbers were too high, and made a public records request for detailed numbers, which showed more ballots than voters checked in. The part of the software designed to notice duplicates had not been installed, and there was no automated checking that the installation was right. In a 2022 election in DeKalb County, GA, a candidate who actually won appeared to lose, after votes were not counted for her in some precincts, because another candidate withdrew, and programming did not categorize votes correctly.