CanadaWhat is the 'discoverability rule' for limitation periods in accident claims?
The discoverability rule means the limitation period for an accident claim starts when you knew or ought to have known that you had a legal claim—not necessarily from the date of the accident.
What the Law Says
Canadian limitation periods are generally set by provincial legislation, but the Supreme Court of Canada has established a common law principle—the discoverability rule—that governs when those periods begin to run.
The discoverability rule is a judge-made principle that modifies strict time limits. It holds that a limitation period does not begin on the date of the accident itself, but rather on the date the plaintiff knew—or, through reasonable diligence, ought to have known—(1) that the injury occurred, (2) that it was caused by the defendant’s act or omission, and (3) that a court action would be an appropriate remedy.
This rule applies across Canada in negligence-based accident claims unless a statute expressly excludes it. No specific federal or Ontario statute text was provided in the prompt, so no statutory quotes are included here.
What Courts Have Said
The Supreme Court of Canada confirmed the discoverability rule as a general principle of limitation law in a landmark motor vehicle accident case.
The Court held that for negligence claims arising from motor vehicle accidents, the limitation period under Ontario’s Limitations Act begins not on the date of the accident, but when the plaintiff discovers—or reasonably should have discovered—the injury, its cause, and the appropriateness of a legal remedy. The Court rejected a rigid 'accident date' start and affirmed that fairness requires considering the plaintiff’s actual or constructive knowledge.
What to Do
Document all symptoms, medical visits, and communications related to your injury — even if mild at first.
Consult a lawyer within 2 years of when you first realized your injury was serious and likely caused by someone else’s negligence.
Do not assume the clock started on the accident date — courts will assess when you reasonably should have known.
If your injury developed gradually (e.g., chronic pain, delayed diagnosis), the limitation period may start much later than the accident.
Sources
Not legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.