What happens to the limitation period if I don't know who to sue until later in Ontario?

Ontario's discoverability rule under the Limitations Act, 2002 generally means the two-year limitation clock doesn't start running until a claimant knew, or reasonably should have known, not just that they were harmed, but also who was responsible. If a claimant genuinely doesn't know, and couldn't reasonably have discovered, the identity of the person or company responsible for the harm until later, discoverability can delay when the clock starts, even though the underlying harm itself may have been apparent much earlier.

This is different from a claimant who knows harm occurred but is simply slow to investigate who caused it; courts generally expect a claimant to make reasonable efforts to identify a responsible party once they know they've been harmed, rather than waiting indefinitely and later claiming ignorance. Where identity genuinely can't be determined despite reasonable efforts, claims are sometimes started against an unidentified defendant using a placeholder name, with the pleading later amended once the responsible party is properly identified through further investigation or a court-ordered disclosure process. Because what counts as "reasonable" diligence is assessed on the facts, documenting genuine efforts made to identify a defendant strengthens a later argument that discovery was properly delayed.