How Long Do You Have to Sue in Ontario? A Plain-Language Guide to Limitation Periods

One of the most important — and most overlooked — questions in any legal problem is simply: how long do I have to do something about it? In Ontario, the answer is usually governed by a deadline called a limitation period. Miss it, and a court can dismiss your case no matter how strong it is. Here is a plain-language guide to how these deadlines work.

The general rule: two years

Most civil claims in Ontario fall under the Limitations Act, 2002. The basic rule (section 4) is that you have two years to start a lawsuit. If you miss that window, the other side can ask the court to throw the case out on the deadline alone — even if you would otherwise have won. That is why it helps to treat a legal problem as time-sensitive from the very beginning.

When does the two-year clock start?

The two years usually does not run from the date of the event itself, but from the day you "discovered" the claim (section 5). You are treated as having discovered a claim when you knew — or a reasonable person in your position ought to have known — all of the following: that some loss or injury occurred; that it was caused, at least in part, by another person's act or omission; who that person is; and that starting a court proceeding would be an appropriate way to seek a remedy.

In everyday terms, the clock generally starts when you realize (or reasonably should realize) that you were harmed, roughly who is responsible, and that suing makes sense. For an obvious event like a car crash, that is often the date of the accident. For something hidden — a latent defect in a building, or a professional's error you only find out about later — the clock may start much later.

The 15-year "hard stop"

There is also an ultimate limitation period of 15 years (section 15). It runs from the day the act or omission happened, regardless of when you discovered the problem. This is a firm outer limit: even if you did not — and could not have — known about your claim, once 15 years pass from the underlying event, the claim is generally gone. In most cases the two-year discovery rule is what matters, but the 15-year cap can be decisive for long-buried claims.

Short deadlines that catch people by surprise

Some claims carry much shorter notice deadlines that are separate from — and earlier than — the two-year limitation period. Two common examples involve slips and falls:

Snow and ice on private property. Since a 2020 change to the Occupiers' Liability Act, a person injured by snow or ice generally must give the occupier (and any snow-removal contractor) written notice of the claim within 60 days of the injury. There are limited exceptions — for example, where the fall caused a death, or where a judge accepts that there was a reasonable excuse for the delay and the other side was not prejudiced.

Municipal sidewalks. If you are hurt because a municipality failed to keep a sidewalk in good repair, the Municipal Act, 2001 generally requires written notice to the municipality within 10 days of the incident. Ten days passes quickly, which is why getting advice early can matter enormously.

These notice rules do not replace the two-year deadline to actually start a lawsuit — they are extra, earlier steps, and missing them can end a claim before it begins.

Situations where the rules are different

Minors and people who are incapable. The basic two-year clock generally does not run while an injured person is under 18 and has no litigation guardian, or while a person is incapable of bringing a claim. The clock can begin once that situation changes.

Claims with no limitation period. A few claims are not subject to any limitation period at all. For example, claims based on sexual assault can be brought at any time under the Act.

Contracts, insurance and other statutes. Insurance policies, contracts, and specific statutes can set their own — sometimes shorter — deadlines, and certain business parties can agree to vary limitation periods within limits. Never assume the default two years applies without checking.

The practical takeaway

Limitation periods are unforgiving, and the safest assumption is that your deadline is sooner than you think. If you believe you may have a claim — or you have suffered an injury, received a demand, or been served with something — it is worth getting advice early, while there is still time to investigate, preserve evidence, give any required notice, and file if necessary. Waiting is one of the most common ways that good claims are lost.

This article is general information about Ontario law and is not legal advice. Limitation periods depend heavily on the specific facts, and the law can change. Anyone who may have a claim should speak promptly with a qualified Ontario lawyer or licensed paralegal about their own situation.