- Ontario has a basic limitation period running from when a claim is discovered.
- Discoverability can postpone the start, but it is not an open-ended extension.
- An ultimate limitation period caps the delay regardless of discovery.
- Different claims and defendants have different rules, and some notice periods are far shorter.
Why this comes first
A limitation defence does not engage with the merits. A claim outside the period fails even if it would otherwise have succeeded entirely.
It is the first thing a defendant’s lawyer checks and it should be the first thing a plaintiff’s lawyer confirms. Missed limitation periods are among the most common serious errors in civil practice.
The basic period
The Limitations Act, 2002 sets a basic limitation period running from the day the claim was discovered.
A claim is discovered on the day the person first knew, or ought reasonably to have known, that the injury, loss or damage had occurred; that it was caused by an act or omission; that the act or omission was that of the person against whom the claim is made; and that a proceeding would be an appropriate means to seek a remedy.
All four elements matter. The last in particular has produced significant case law, because it can postpone the start where litigation was not yet an appropriate response, for example while a defendant was actively attempting to remedy the problem.
Discoverability is not unlimited
The reasonable-discovery element imports an objective standard. A plaintiff who ought to have known cannot rely on not having asked.
That means a person aware of a problem is expected to investigate with reasonable diligence. Waiting to be told, or hoping the matter resolves, does not reliably postpone the clock.
There is also an ultimate limitation period running from the day of the act or omission, regardless of discovery, with limited exceptions. It exists to prevent indefinite exposure.
Where the rules differ
Several categories depart from the basic rule and are easily missed:
- Claims against municipalities frequently require written notice within a very short period, which is a notice requirement separate from and shorter than the limitation period.
- Certain claims against the Crown have their own notice provisions.
- Some statutes contain their own limitation periods that override the general Act.
- Certain claims, including some based on sexual assault, are not subject to a limitation period.
- Periods do not run while a person is a minor or is incapable, subject to the rules on litigation guardians.
Because of these variations, the safe approach is to check the specific claim rather than apply the basic period by default.
Stopping the clock
Issuing a claim stops it. Nothing else reliably does.
Parties can agree to suspend or extend a limitation period in defined circumstances, and a tolling agreement is a common tool during settlement negotiation. It must be documented properly.
An acknowledgment of liability in writing can, in some circumstances, restart the period. The requirements are technical.
What does not stop the clock: sending a demand letter, negotiating, engaging in mediation, or being told the other side is looking into it. Files are lost this way with some regularity.
Practical consequences
For a plaintiff: get advice early. Identifying the correct defendant is part of the analysis, and adding a defendant after the period has run is difficult and often impossible.
For a defendant: a limitation defence should be identified immediately and pleaded, since it can dispose of a claim without a trial on the merits.
For both: where the discovery date is genuinely arguable, the limitation issue may itself require a hearing, and the evidence about what the plaintiff knew and when becomes central.
Common questions
Does sending a demand letter preserve my claim?
No. Only issuing a proceeding stops the limitation period, subject to a properly documented tolling agreement.
When does the clock start if I did not know who caused the loss?
Discovery includes knowing the act was that of the person against whom the claim is made, so the period may not begin until the defendant is reasonably identifiable.
Are there claims with no limitation period?
Yes, including certain claims based on sexual assault. These are specific exceptions rather than a general principle.
Can a limitation period be extended by agreement?
Parties can agree to suspend or extend in defined circumstances. It should be documented carefully rather than assumed from correspondence.
Contacting us does not create a solicitor-client relationship. Please do not send confidential information until we have confirmed we can act for you. We aim to reply within 2 business days. Sending this form does not meet any court deadline or limitation period.
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