SCC Clarifies When Administrative Errors Are “irregularities” Requiring Annulment Of Election

In Sinclair-Desgagné v. Canada (Chief Electoral Officer), 2026 SCC 31, the Supreme Court of Canada, in a 6-3 decision, annulled the 2025 federal election in the electoral district of Terrebonne, Québec, after concluding that a mail-in ballot was not counted because of a serious administrative error by Elections Canada. The majority held that an “irregularity” under s. 524(1)(b) of the Canada Elections Act includes a serious administrative mistake, even where the mistake is honest and unintentional. Because the lost vote equalled the one-vote margin of victory, the election result was left in doubt and the election was annulled.

The decision is significant not only because it resulted in the rare annulment of a federal election, but because it clarifies how courts should balance electoral integrity and voter enfranchisement under the Canada Elections Act. The majority emphasized that serious administrative errors by election officials can undermine the right to vote even where there