How Long Do You Have to Sue in Ontario? Limitation Periods

One of the most important — and most misunderstood — rules in civil litigation is the limitation period: the window of time within which you must start a lawsuit. Miss it, and you almost certainly lose your right to sue, no matter how strong your case is. Ontario's rules on limitation periods are set out in the Limitations Act, 2002, and they are not always as straightforward as they appear.

If you believe you have a legal claim against someone, the first question any lawyer will ask is: when did you discover the problem? The answer determines your deadline.

The Basic Two-Year Limitation Period

For most civil claims in Ontario, you have two years from the date you discovered — or ought reasonably to have discovered — that you have a claim. This is known as the basic limitation period.

"Discovered" has a specific legal meaning. Under the Limitations Act, 2002, a claim is discovered on the earliest date a person knew, or a reasonable person in their position ought to have known, all of the following:

1. That an injury, loss, or damage occurred;
2. That it was caused or contributed to by an act or omission;
3. That the act or omission was that of the person against whom the claim is made; and
4. That a proceeding would be an appropriate means to seek to remedy it.

In plain language: the clock starts when you knew (or should have known) that you had a legal problem and who was responsible.

Why "Discoverability" Matters

The discoverability rule exists because some harms are not immediately obvious. A construction defect may not appear until years after a building is completed. A professional's negligent advice may not cause visible financial harm until later. A fraudster may actively conceal their wrongdoing.

In those situations, the two-year period does not begin the moment the act occurred — it begins when the damage became apparent (or when a reasonable person would have taken steps to uncover it). This is protective for plaintiffs, but it does not mean you can wait indefinitely once you have reason to suspect a problem. Courts expect you to act reasonably to investigate, not to sit on a potential claim.

The practical rule: as soon as you have a reason to believe someone has caused you harm, consult a lawyer. Do not wait until you have gathered all the evidence.

The 15-Year Ultimate Limitation Period

Even where the discoverability rule delays the start of the basic two-year period, Ontario imposes an ultimate limitation period of 15 years from the day the act or omission occurred. This is an absolute backstop.

With very narrow exceptions, no civil claim can be brought more than 15 years after the act that gave rise to it — regardless of when the plaintiff discovered (or could have discovered) the harm. The ultimate limitation period reflects a policy that defendants should not face indefinite exposure to liability.

Common Exceptions and Special Rules

The Limitations Act, 2002 carves out a number of exceptions. These are complex and fact-specific; only a summary follows.

Claims Involving Minors and Persons Under Disability

The basic two-year period does not run while the potential plaintiff is a minor (under 18) or does not have the legal capacity to make decisions (for example, due to cognitive impairment). Once capacity is restored — or the minor turns 18 — the two-year clock begins. However, the 15-year ultimate limitation period still applies.

Sexual Assault and Childhood Abuse

Ontario removed limitation periods entirely for claims of sexual assault and certain other misconduct, recognizing that survivors often need years before they are able to come forward. These claims are not subject to the basic two-year or ultimate 15-year periods.

Government and Public Bodies

Suing a municipality, government ministry, or other public body often involves notice requirements and shorter timelines under specific statutes. The Municipal Act, 2001, for example, imposes obligations to give notice of certain claims within a strict period. Always confirm whether a special regime applies before treating the standard two-year period as your deadline.

Construction Claims

Claims arising from construction work — including claims under the Construction Act — have their own limitation and preservation rules. Liens, in particular, must be preserved within strict timeframes after last work. These deadlines do not follow the standard Limitations Act framework and missing them can be fatal to a claim.

Contractual Limitation Periods

Contracts sometimes contain their own limitation clauses — for example, an agreement requiring any claim to be brought within one year. Ontario law permits some contracting out of limitation periods (subject to restrictions), so you must read any contract carefully.

Acknowledgment and Part Payment

If the person who owes you a debt acknowledges it in writing, or makes a payment toward it, the two-year clock can restart. This rule has narrow technical requirements; do not rely on it without legal advice.

What Happens If You Miss the Limitation Period?

Typically, a defendant who is sued after the limitation period has expired will raise the expired limitation as a complete defence. Courts take this seriously — a claim brought outside the limitation period will generally be dismissed, even if the underlying facts are undisputed.

There is almost no cure once the limitation period has passed. A court has very limited discretion to extend it, and that discretion is rarely exercised. This makes early action essential.

Why Acting Early Matters

Limitation periods are not the only reason to act quickly. Evidence deteriorates over time: witnesses forget, documents are lost, electronic records are deleted, and physical evidence is destroyed. The stronger your claim feels today, the harder it may be to prove two years from now.

Starting the limitation-period clock early also gives you options — time to send a demand letter, explore settlement, and decide whether litigation is the right path before committing to the cost and effort of a lawsuit.

Frequently asked questions