Mailed your ballot and it never arrived? Why Canada’s top court cancelled an election over one vote

For voters in Canada, especially those who vote by mail. As of October 2026.

In the federal riding of Terrebonne, Quebec, one mail-in ballot never reached Elections Canada. The winner’s margin was exactly one vote. The Supreme Court of Canada annulled the election, and its written reasons explain why, and why three judges disagreed.

What happened

• For the federal election of April 28, 2025, an Elections Canada employee printed the wrong postal code on prepaid return envelopes for several mail-in ballots in Terrebonne. By his estimate, at least 40 electors were affected.
• He found the error over three weeks before election day, but did not report it to his supervisors or contact the affected electors.
• After a judicial recount, the election was decided by one vote.
• Shortly after election day, one voter’s mail-in ballot came back to her undelivered. It was never counted.

What the court decided

• On February 13, 2026, a majority of the Supreme Court allowed the appeal and annulled the election, with reasons to follow. The reasons, 2026 SCC 31, were released on September 18, 2026. The vote was 6 to 3.
• Writing for the majority, Justice Jamal applied the three-step test from Opitz v. Wrzesnewskyj: was there an irregularity, did it affect the vote count, and should the election be annulled?
• An irregularity can be a serious administrative error that is honest and unintentional. Elections Canada caused this error and had the ability and responsibility to fix it.
• The court did not look at who the voter said she voted for, because of ballot secrecy. What mattered was the count: one lost vote, equal to the one-vote margin, left the winner in doubt.
• The majority said this situation is narrow, and that annulling an election will remain extremely rare.

The dissent: whose job is it to make sure the ballot arrives?

Justices Karakatsanis and Martin, with Justice Moreau, would have dismissed the appeal. They pointed to the Canada Elections Act, which says a voter using a special ballot has the sole responsibility to ensure the ballot is received in time. In their view, the mistake was limited and inadvertent, and setting the bar this low would put election results at risk.

What this means for you as a voter

1. Mail your ballot early. The law still places the responsibility on mail-in voters to make sure the ballot is received before the polls close.
2. Track it. The lower court noted that Elections Canada gives mail-in voters a tracking number.
3. If it has not arrived, act before voting day. The lower court noted the voter could have contacted her riding’s special voting rules administrator to ask for permission to vote in person on polling day.
4. Check Elections Canada’s special ballot instructions for the current rules before you vote by mail.

The point to remember

Canada’s top court annulled a federal election because an Elections Canada error, which it knew about and could have fixed, cost one voter her vote in a race decided by one vote. Voting by mail still puts the duty on you to make sure your ballot arrives, so mail early and track it.

Check the official pages before you act:

• Supreme Court of Canada, Case in Brief: Sinclair-Desgagné v. Canada (Chief Electoral Officer)
• Supreme Court of Canada, Sinclair-Desgagné v. Canada (Chief Electoral Officer), 2026 SCC 31 (full reasons)

Join the conversation

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This article is general information on Canadian law, as of October 2026. It is not legal advice and does not create a representative relationship. Always consult a licensed legal professional for your specific situation.