Brazil’s electronic voting system is checked through several different procedures before, during and after elections. The Tribunal Superior Eleitoral (TSE), Brazil’s electoral authority, describes tests of software and equipment, checks that installed systems are authentic, and a controlled test in which known paper-ballot choices are entered into a selected machine and compared with its report. Each procedure addresses a limited question; none should be treated on its own as proof of every aspect of an election.
How does Brazil’s electronic voting system work?
Brazilian voters cast their choices using an electronic voting machine, known in Portuguese as an urna eletrônica. The TSE’s audit procedures do not all examine the same thing: some review software before an election, some check the systems installed in machines, and others test how a machine records a known set of entries.
That distinction matters. A test using specially prepared paper ballots is not a recount of ballots cast in ordinary polling sections. Likewise, confirming that a sampled machine has an authentic software installation does not by itself test how that machine accounts for a set of known choices.
How are votes and voting systems audited?
The TSE describes a set of audit opportunities across the election cycle. The table summarizes the purpose and limits of the principal procedures described by the authority; it is not a claim that any one procedure proves every property of the election.
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| Procedure | When and what it examines | What it can help establish |
|---|---|---|
| Public Security Test (PST) | Technical investigators exercise electoral hardware and software before an election; a later confirmation phase checks whether suggested improvements were incorporated. | Potential weaknesses or improvements identified through the test. The TSE reported that the 2025 confirmation phase found no issue that weakened vote secrecy or integrity. |
| Source-code inspection and development monitoring | Eligible entities inspect electoral-system software during a scheduled period before an election and may ask technical staff for clarification. | Allows review of the software and its development; it is not a test of every machine’s election-day operation. |
| Digital sealing and signing | Procedures are applied to prepared electoral systems before use. | Intended to establish that prepared systems are the authorized versions. |
| Authenticity test | On election day, a sample of machines is checked for authenticity and integrity of installed systems, including digital signatures and summaries. | Whether sampled machines have the expected authentic systems installed; it does not compare a known set of entered votes with a machine’s output. |
| Controlled integrity test | Known choices on paper ballots are entered into a selected machine under observation; its report is compared with the paper tally. | Whether that test machine’s output matches the choices entered during the test. |
| Biometric integrity-test modality | A 2026 rule provides for a modality in which volunteers may consent to use of their biometrics to enable the test machine after they have voted officially. | A way to conduct an integrity test using the specified biometric procedure; it remains distinct from the authenticity check. |
| TCU procedural oversight for 2026 | The Federal Court of Accounts (TCU) announced that it would accompany integrity-test procedures in all 27 federative units. | External, complementary monitoring focused on whether prescribed procedures are followed, not a substitute for those procedures. |
The TSE’s 2024 overview reported that its 2023 Public Security Test involved 33 investigators who carried out 35 plans. Those are participation counts reported by the TSE, not measures of election accuracy. In a separate sampling procedure described in its 2024 report, the TSE said up to 6% of machines prepared for each electoral zone were randomly selected from voting and contingency machines. That percentage applies to the procedure described there, not to every audit or necessarily to later elections.
Can someone inspect the voting software?
The TSE says eligible fiscalizing entities can inspect electoral-system source code and monitor development during the scheduled inspection period. Its list includes political and public institutions, professional bodies, universities and accredited Brazilian civil-society organizations. The TSE’s 2024 overview says the inspection is scheduled in advance and provides access to the set of ballot-box software. Eligibility and timing can depend on the rules for a particular election.
The TSE describes inspection as providing access to electoral software, opportunities to test the electronic voting machine and access to technical staff for clarification. It is a review opportunity before the election—not, by itself, confirmation that every deployed machine behaved correctly on election day.
What happens in the controlled integrity test?
- Machines and locations are selected. According to the TSE’s explainer, selected machines have already been prepared for ordinary polling and sealed. Sections for the test are chosen in a public ceremony involving electoral authorities and fiscalizing entities; a draw is used as needed to reach the required number. The selected machines go to public test locations.
- Test choices are written on paper. Volunteers and representatives prepare paper ballots showing known choices. These ballots are test materials, not a tally of ordinary votes cast in polling sections.
- The choices are entered into the machine. During official voting hours, auditors read the paper ballots aloud and enter the choices into the selected machine. The process is recorded in audio and video and observed by auditors.
- The electronic and paper results are compared. At the end, the machine emits a Boletim de Urna (BU, or ballot-box report). Auditors compare that report with the paper tally of the test ballots.
The test asks whether the selected device’s report matches the known choices entered under those test conditions. It is not a recount of all votes cast in regular polling sections, nor does it alone establish the security or accuracy of every machine in the election.
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How is an authenticity test different from an integrity test?
These names refer to different checks. The integrity test compares a known set of test choices with a machine’s output. The authenticity test samples machines on election day to check whether the installed systems are authentic, including their digital signatures and summaries. One tests the handling of known entries; the other checks the identity and integrity of installed software.
They sit alongside pre-election source-code review, public security testing and the procedures for sealing and signing systems. Together, these provide different opportunities to examine systems and machine operation, but their conclusions should not be stretched beyond what each procedure actually checks.
What is the biometric integrity test?
A March 2026 amendment to the TSE’s audit rules defines both a controlled-environment integrity test and a biometric modality. In the biometric modality, volunteers can consent to their biometrics being used to enable the test machine. The volunteers are invited after they have cast their official vote. This is a way of enabling the machine for the audit procedure; it does not mean their official votes are the test ballots.
The same amendment requires a consolidated report of integrity-test results to be published on the Electoral Justice website within 90 days after the second round. For a particular election, consult the actual report and election dates rather than assuming a result or publication date.
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What have the TSE’s reported tests found?
In its August 2026 explanation of the integrity test, the TSE quoted Júlio Valente, its Secretary of Information Technology, saying that since 2002 the laboratory tests had not recorded a result different from what was entered into the electronic ballot box. That is a statement attributed to Valente and reported by the TSE; it should not be presented as an independent evaluation of all election outcomes.
Separately, in a 15 May 2026 report on the confirmation phase of the 2025 Public Security Test, the TSE said investigators checked whether suggested improvements had been incorporated and that no identified finding weakened vote secrecy or integrity. This describes the TSE’s account of that test, rather than an independent assessment.
On 2 October 2026, the TSE announced that the TCU would accompany integrity-test procedures in all 27 federative units during the 2026 election. The TSE described this as complementary external oversight under a cooperation agreement, focused on checking compliance with established procedures. The announcement describes planned monitoring; it should not be treated as confirmation that the monitoring has been completed.
Does every voter receive a paper record of their vote?
The TSE material described here establishes that paper ballots are used in a separate controlled integrity test. It does not establish whether an ordinary voter receives a voter-verifiable paper record of their own vote. The existence of test ballots should not be taken as evidence either way about an individual voter’s record.
How to interpret the audit framework
The most useful way to read an audit claim is to ask what was tested, when it was tested, which machines or software were involved, and what result the procedure can support. The TSE is the authority for the rules and procedures described here, and its accounts explain how it says those processes work. They are not, by themselves, an independent evaluation of the system’s overall effectiveness or of every election outcome.
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