Canada’s highest court has stated that Elections Canada made a significant administrative mistake that could have undermined the integrity of the electoral process by failing to address issues with mail-in ballots in a Montreal-area riding before the 2025 federal election. The Supreme Court of Canada nullified the election results of the Terrebonne riding in a ruling in February and disclosed the rationale behind their decision on Friday.
The court emphasized that the decision to call for a new election “bolsters public confidence in the electoral system by confirming that a federal election should not be influenced by identifiable and correctable official errors.” The initial winner in the Terrebonne riding, Liberal candidate Tatiana Auguste, was declared victorious by a one-vote margin over incumbent Bloc Québécois candidate Nathalie Sinclair-Desgagné in April 2025.
The election results were challenged by the Bloc candidate, who requested a byelection after a supporter reported that her attempt to vote by mail using a special ballot had not been counted. The voter, Emmanuelle Bosse, revealed that her special ballot was sent back to her mailbox due to a postal code error on a label provided by Elections Canada.
Although a Superior Court judge initially denied Sinclair-Desgagné’s plea for a new election, the Supreme Court overturned that decision through a split verdict issued in February, resulting in a byelection that Auguste won on April 13.
In the majority opinion, Justice Mahmud Jamal highlighted that an Elections Canada staff member had been aware for weeks that some voters received envelopes with incorrect postal codes but did not take corrective measures. The court found that Elections Canada was at fault for failing to rectify the error, despite knowing about it and expecting affected voters to be contacted by staff.
An Elections Canada employee had dispatched misaddressed envelopes for mail-in ballots to approximately 40 electors and noticed the mistake over three weeks before the election day without reporting it to supervisors. The employee assumed the error was inconsequential because the Terrebonne polling station continued to receive completed special ballots with the postal code error.
The agency stated that it had reviewed its special ballot process post-election and implemented changes. Elections Canada noted it would carefully assess the Supreme Court ruling before determining further steps. The decision was split 6-3, with the majority underscoring that the threshold for overturning an election remains stringent and does not open the door to numerous challenges for every election-related error.