Ontario Limitation Periods: A Complete Guide for Law Firms

Why Limitation Periods Are the Most Dangerous Deadline in Law

There are deadlines in legal practice, and then there are limitation periods. Miss a filing deadline and you can usually get an extension. Miss a limitation period and the claim is extinguished — permanently. For the client, it means no recourse. For the lawyer, it means a potential negligence claim that will be very difficult to defend. In Ontario, the consequences of limitation period errors are outsized because the Limitations Act, 2002 introduced a regime that is deceptively simple in structure but riddled with exceptions and nuance that can catch even experienced practitioners off guard.

This guide provides a comprehensive overview of Ontario's limitation period regime, with a focus on the provisions that most commonly generate errors in practice.

The Basic Limitation Period: Two Years from Discovery

Section 4 of the Limitations Act, 2002 establishes the basic limitation period: a proceeding shall not be commenced more than two years after the day on which the claim was discovered. This is the rule that applies to most civil claims in Ontario, including negligence, breach of contract, and most tort claims.

The two-year period does not begin running from the date of the events that gave rise to the claim. It begins running from the date the claim was "discovered" — a term that has a specific statutory meaning under Section 5 of the Act.

The Discoverability Rule: Section 5

Under Section 5, a claim is discovered on the earlier of:

• The day on which the person with the claim first knew that the injury, loss, or damage had occurred; that it was caused by or contributed to 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 remedy.
• The day on which the person with the claim ought to have known these things, had they exercised reasonable diligence.

The discoverability analysis is fact-intensive and frequently litigated. Key principles from Ontario case law include:

• Constructive knowledge is sufficient. A person cannot avoid the commencement of the limitation period by willfully ignoring the facts that would reveal their claim.
• The "appropriate means" requirement has generated significant jurisprudence. In some cases, courts have held that a claim was not discovered until other remedies (such as insurance claims or internal grievance processes) were exhausted or proved inadequate.
• Medical discovery is treated specially. In personal injury claims, the limitation period typically does not begin running until the plaintiff knows the full extent and implications of their injuries — which can be months or years after the incident.
• For claims against professionals (including lawyers), the limitation period may not begin until the client discovers or ought to have discovered the professional's error or negligence.

The Ultimate Limitation Period: 15 Years (Previously 10 Years)

Section 15 of the Limitations Act, 2002 establishes an ultimate limitation period — a hard deadline beyond which no claim can be brought, regardless of discoverability. Originally set at 10 years, amendments have adjusted this period. The ultimate limitation period runs from the date of the act or omission that gave rise to the claim, not from the date of discovery.

The ultimate limitation period serves as a backstop. Even if a claimant could argue that they did not discover their claim until many years after the events in question, the ultimate limitation period provides an absolute deadline. This is particularly relevant in professional negligence claims, product liability cases, and latent injury claims where discoverability may be delayed by years.

Key Exceptions and Special Rules

Municipal Claims: The Act Does Not Apply

The Limitations Act, 2002 does not apply to claims against municipalities. Claims against Ontario municipalities are governed by the Municipal Act, 2001 and the City of Toronto Act, 2006, which require written notice of a claim within 10 days of the event (with limited discretion to extend) and commencement of proceedings within the applicable limitation period under common law principles. This 10-day notice requirement is one of the most commonly missed deadlines in Ontario practice.

Sexual Abuse Claims

Section 16(1)(h) provides that there is no limitation period for a proceeding based on a sexual assault. This exception was introduced to address the reality that survivors of sexual abuse often take many years to come forward, and it reflects a policy judgment that access to justice should not be denied on limitation grounds in these cases. The exception applies regardless of when the assault occurred.

Claims by Persons Under a Disability

Section 7 provides that the limitation period does not run during any time in which the person with the claim is a "person under a disability" — defined as a minor or a person who is incapable of managing their property. The limitation period begins running when the person ceases to be under a disability (turns 18 or has a capacity restoration).

Fraud and Concealment

Section 5(3) provides that a person shall not be regarded as having discovered a claim if the defendant fraudulently concealed the facts on which the claim is based. The limitation period does not begin running until the claimant discovers, or ought to have discovered, the fraud. This exception can extend the limitation period significantly.

Acknowledgement and Partial Payment

Sections 13 and 14 provide that the limitation period can be reset by an acknowledgement of the claim or a partial payment. An acknowledgement must be in writing, signed by the person making it, and must refer to the claim. A partial payment has the same effect. Practically, this means that obtaining a written acknowledgement or partial payment from a debtor can restart the limitation clock.

The Dates Lawyers Most Often Get Wrong

Based on our analysis of limitation period errors in Ontario practice, the following are the most common mistakes:

• The 10-day municipal notice requirement. Lawyers handling motor vehicle accidents, slip-and-fall claims, or any matter possibly involving a municipality must assess municipal liability immediately and serve notice within 10 days. Missing this deadline is frequently fatal to the claim.
• Discoverability in gradual injury cases. Occupational disease, environmental contamination, and gradual property damage claims all present discoverability challenges. The limitation period may not begin when the exposure starts but when the claimant knew or should have known that they had a legally actionable claim.
• The transition between the old Limitations Act and the 2002 Act. Claims that arose before January 1, 2004 (when the 2002 Act came into force) are governed by the old Act, which had different limitation periods and no statutory discoverability provision. Practitioners handling older matters must determine which regime applies.
• Insurance claims vs. third-party claims. The limitation period for a claim against a tortfeasor is generally two years, but the limitation period for an insurance claim may be different and is often set by the policy — sometimes as short as one year.
• Trust claims. Claims to recover trust property have no limitation period under Section 16(1)(a), but practitioners must correctly characterize the claim as a trust claim rather than, for example, a breach of contract claim subject to the basic two-year period.

Best Practices for Limitation Period Management

• Calculate and diary every limitation date immediately upon being retained. Do not defer this to a later date.
• Apply a safety margin. Many firms diary limitation dates 90-120 days before the actual expiry, with additional alerts at 60 days and 30 days.
• Document your limitation analysis in writing, including the basis for the discovery date you have selected.
• When in doubt, issue and serve a statement of claim. It is far easier to discontinue a claim than to revive one after a limitation period has expired.
• Have a second lawyer review the limitation analysis for every new file. Fresh analysis catches errors that familiarity can obscure.

How LexIntake Helps

LexIntake's Deadline Calculator automatically calculates limitation dates based on Ontario's Limitations Act, 2002, applying the correct basic and ultimate limitation periods and flagging special rules for municipal claims, disability tolling, and other exceptions. Our Case Timeline tool integrates limitation dates with court deadlines, discovery deadlines, and client milestones — providing a single view of every critical date on every file. Automated alerts ensure that no deadline is missed, and audit trails document your limitation analysis for protection against negligence claims.