Supreme Court of Canada invalidates Terrebonne election results

The Supreme Court of Canada has explained its decision to invalidate the results of the 2025 federal election in the Montreal-area riding of Terrebonne. The court ruled that annulling the result was necessary to maintain public trust in the electoral process and to ensure that a federal election is not decided by a known and correctable administrative error.

In the original April 2025 election, Liberal candidate Tatiana Auguste was declared the winner over Bloc Québécois candidate Nathalie Sinclair-Desgagné by a single vote. The decision followed a challenge by the Bloc Québécois after a supporter reported that a special mail-in ballot was never counted.

Writing for the majority, Justice Mahmud Jamal noted that an Elections Canada employee was aware for weeks that certain voters had been sent envelopes with incorrect postal codes, yet the agency failed to take corrective action. While a Superior Court judge had previously rejected the request for a new election, the Supreme Court reversed that ruling in a split decision.