Brazil’s electronic voting system is checked through several procedures before, during and after an election. The Tribunal Superior Eleitoral (TSE), Brazil’s electoral authority, describes reviews of the software, tests intended to expose security weaknesses, checks that installed systems are authentic, and operational tests in which known choices are entered into selected machines and compared with their output. Each procedure addresses a different question; none by itself establishes every property of the entire election.
How does Brazil’s electronic voting system work?
Voters cast their choices on an electronic ballot box, or urna eletrônica. The audit procedures described by the TSE examine different parts of the system and its operation: whether software can be inspected and tested, whether the software installed on sampled machines is authentic, and whether a machine records a known set of choices as entered.
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The distinction matters because “audit” is not one single test. A software review before an election, an election-day check of installed systems and a controlled test of vote counting have different methods and limits. The TSE is the source for the procedures and findings described here; those institutional accounts explain how its processes are intended to work, rather than constituting an independent evaluation of their effectiveness.
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The TSE describes a lifecycle of checks. Before an election, eligible entities can inspect electoral software, and technical investigators can test the system for potential weaknesses. A digital sealing and signing process is intended to identify prepared systems as authorized versions. On election day, separate procedures check system authenticity and machine operation. Results from integrity tests are also subject to publication requirements under the 2026 rules.
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| Procedure | When | What it examines |
|---|---|---|
| Public Security Test (PST) | Before an election, with a later confirmation phase | Technical investigators exercise the system and can identify potential improvements. |
| Source-code inspection and development monitoring | During a scheduled pre-election inspection period | Electoral software, with access for eligible inspecting entities. |
| Digital sealing and signing | As systems are prepared for an election | Whether prepared systems are the authorized versions. |
| Authenticity test | Election day | Whether systems installed in sampled machines are authentic, including checks of digital signatures and summaries. |
| Integrity test | During election hours at designated test locations | Whether a selected machine’s electronic output matches a known set of choices entered for the test. |
| TCU monitoring announced for 2026 | Planned for the 2026 election | Whether integrity-test procedures are carried out according to the prescribed steps. |
These checks are complementary, not interchangeable. For example, a machine’s successful count of test entries does not answer whether its installed software is authentic; that is the purpose of the separate authenticity procedure.
Can the electronic ballot box be checked?
Yes. The TSE says eligible fiscalizing entities—including political and public institutions, professional bodies, universities and accredited Brazilian civil-society organizations—can participate in specified oversight activities. For source-code inspection, the TSE’s 2024 overview says access is scheduled in advance and covers the set of ballot-box software. Eligibility and timing for a particular election depend on its applicable rules.
The TSE’s overview of the 2023 Public Security Test reported that 33 investigators carried out 35 test plans. Those are participation and activity counts, not measurements of vote accuracy. In its 15 May 2026 account of the confirmation phase of that test, the TSE said investigators checked whether suggested improvements had been incorporated and that no identified finding weakened vote secrecy or integrity. That is the TSE’s report of the test’s outcome.
The TSE’s 2024 account also describes one sampling procedure that covered up to 6% of machines prepared for each electoral zone, randomly selected from voting and contingency machines. That figure applies to the procedure described in that account; it should not be treated as a universal sampling rate for every audit or later election.
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What happens in the integrity test?
In the controlled integrity test, auditors use paper ballots with known choices to check the counting behavior of a selected machine. The TSE’s August 2026 explainer describes the process as follows:
- Machines selected for the test have already been prepared for ordinary polling and sealed.
- Sections for testing are chosen at a public ceremony involving electoral authorities and fiscalizing entities; a draw is used when needed to reach the required number. Selected machines are taken to public test locations.
- Volunteers and representatives prepare paper ballots with known choices. During official voting hours, auditors read the choices aloud and enter them into the selected machine. The process is recorded in audio and video and observed by auditors.
- At the end, the machine emits a Boletim de Urna (BU), or ballot-box report. Auditors compare that electronic report with the paper tally of the choices entered.
The comparison tests whether that machine’s reported count matches the known entries made under test conditions. It is not a recount of all votes cast in ordinary polling sections.
The 2026 rules formally define two integrity-test modalities. The controlled modality uses previously filled paper ballots. In the biometric modality, volunteers may consent to using their biometrics to enable the test machine; they are invited after casting their official vote. The biometric modality is a way to conduct the test, not a substitute for the separate authenticity check.
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The integrity test asks whether a selected machine accounts for known choices in line with the entries made during a controlled test. The authenticity test samples machines on election day to check whether the systems installed on them are authentic, including by checking digital signatures and summaries. One tests a machine’s response to known inputs; the other checks the identity and integrity of installed systems.
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In an August 2026 TSE report, its Secretary of Information Technology, Júlio Valente, said that the laboratory tests had recorded no result different from the choices entered for more than 20 years. This is a statement attributed to Valente and reported by the TSE; it should not be read as an independent finding about every aspect of the electoral process.
Who oversees the 2026 integrity tests?
On 2 October 2026, the TSE announced that the Federal Court of Accounts (TCU) would accompany integrity-test procedures in all 27 federative units during the 2026 election. The TSE described the TCU’s role as complementary external oversight under a cooperation agreement, focused on whether prescribed steps are followed. The announcement establishes a plan; it does not by itself confirm that the monitoring has been completed.
Under the TSE’s March 2026 amendment, a consolidated report of integrity-test results must be published on the Electoral Justice website within 90 days after the second round. To assess a particular election, consult the report for that election rather than assuming a result from the rule or announcement.
Does every voter get a paper record of their vote?
The TSE procedures described here do not establish whether an ordinary voter receives a voter-verifiable paper record of their own vote. Paper ballots used in the controlled integrity test are prepared for that separate audit; their use does not show that each voter receives a paper record in ordinary polling.
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