When does Ontario's two-year limitation period actually start running?

Under Ontario's Limitations Act, a claim is "discovered" — and the two-year clock starts — on the earliest day you knew or ought reasonably to have known that an injury, loss, or damage occurred; that it was caused by an act or omission of the person you want to sue; that the act or omission was that of the person you intend to name as a defendant; and that a legal proceeding would be an appropriate means to address the situation.

Courts interpret "ought reasonably to have known" objectively: what would a reasonable person in your situation have known or found out if they had taken reasonable steps to investigate? Deliberately ignoring obvious warning signs does not delay the clock.

In practice, discovery is often straightforward — you know immediately when you suffer a car accident, a missed closing, or a missed payment. It becomes more complex in cases involving hidden defects in a building, a professional's negligent advice whose consequences only became apparent later, or fraudulent concealment by the defendant. In those situations, the date of discovery may be genuinely disputed, and courts assess the evidence carefully.

If you think the limitation period may have started running, do not wait to investigate — consult a lawyer as soon as possible because the legal steps to stop the clock (commencing a proceeding) take time to execute.