Every claim in Ontario is subject to a deadline for when it has to be filed, separate from any deadline you have to respond to one. If a plaintiff waited too long to sue, that alone can be a complete defence — one that doesn't depend on whether their underlying claim was ever valid. This is one of the more technical defences available to a defendant, and also one of the most powerful when it applies.
Ontario's general two-year limitation period
Under the Limitations Act, 2002, most claims in Ontario — including the kinds of debt, contract, and property disputes that make up the bulk of Small Claims Court cases — are subject to a general two-year limitation period. In broad terms, a plaintiff generally has two years from the day the claim was discovered, or reasonably ought to have been discovered, to start a proceeding. See our overview of limitation periods for how this applies from the plaintiff's side, and the filing deadline calculator for a way to estimate specific dates.
Why an expired limitation period is a complete defence
If a limitation period has genuinely expired before the claim was filed, it doesn't matter how strong the plaintiff's case would otherwise have been — the claim can be dismissed on that basis alone. This is what makes it a "complete" defence rather than a partial one: it doesn't reduce the amount owed or shift blame, it ends the case outright, regardless of the underlying facts. That's also why it's worth taking seriously even in a case where you otherwise feel the plaintiff has a point.
Why you have to raise it yourself
A court does not typically comb through a claim looking for a limitation problem on its own initiative. This is generally treated as a defence that has to be pleaded — meaning you need to raise it clearly in your Defence, stating the dates you say matter and why they put the claim outside the limitation period. If you don't raise it, you risk losing the benefit of a defence that may otherwise have ended the case for you.
Discoverability: when the clock actually starts
The two-year clock doesn't always start on the date something went wrong — it generally starts on the date the plaintiff knew, or reasonably ought to have known, that they'd suffered a loss, who caused it, and that a court proceeding would be an appropriate way to address it. This is the discoverability principle, and it means the relevant date can be later than the date of the underlying incident itself — sometimes considerably later, if the loss wasn't immediately apparent.
What can pause the clock, or restart it
A handful of circumstances can affect the calculation. A clear written acknowledgment of a debt or obligation, for example, can restart a fresh limitation period running from the date of that acknowledgment. Certain agreements between the parties, or specific statutory rules for particular claim types, can also affect the timeline. None of this is a reason to assume the general two-year rule doesn't apply to you — it's a reason to look closely at the specific facts and communications in your situation before relying on the defence.
Why getting the dates right matters so much
Because this defence turns entirely on specific dates — when the loss happened, when it was or should have been discovered, whether anything paused or restarted the clock — precision matters far more here than in most other defences. A vague assertion that "this happened a long time ago" won't carry the same weight as a Defence that sets out the actual dates and explains, step by step, why they place the claim outside the limitation period. If the dates are close or genuinely uncertain, that's a good reason to get a second opinion before relying on this defence alone.
Frequently asked questions
What is Ontario's general limitation period?
Two years from the day the claim was discovered, or reasonably ought to have been discovered, under the Limitations Act, 2002. Some claim types have different rules, so the general period isn't automatic in every case.
Will the court automatically dismiss a claim filed after the limitation period expired?
No. A limitation period is generally a defence that must be raised by the defendant, typically in the Defence, rather than something the court checks and applies on its own initiative.
Does it matter when I actually noticed the problem, or only when it happened?
It can matter a great deal. Under the discoverability principle, the clock often starts when the plaintiff knew or reasonably should have known about the loss and who caused it, which isn't always the same date as when the underlying event occurred.
Can an acknowledgment of a debt restart the limitation clock?
It can, in some circumstances. A clear, written acknowledgment of a debt or an obligation can start a new limitation period running from the date of that acknowledgment, which is why the surrounding facts and dates matter so much.