Over the years, I’ve seen it from both sides and the middle of the table, as counsel and now as mediator. It’s the look on a plaintiff’s face during that sinking moment when someone realizes their claim may already be out of time. The law’s two-year clock rarely moves with the body’s pace of recovery, and that disconnect is why I wrote this playbook.

Ontario’s default rule is blunt. You get two years to sue, starting on the day your claim is “discovered.” For personal-injury cases, the Limitations Act, 2002^[1]sets the framework.

Section 4 establishes the basic two-year period:

4 Unless this Act provides otherwise, a proceeding shall not be commenced in respect of a claim after the second anniversary of the day on which the claim was discovered.

Section 5 defines discoverability:

5 (1) A claim is discovered on the earlier of,

(a)  the day on which the person with the claim first knew,

(i)  that the injury, loss or damage had occurred,

(ii)  that the injury, loss or damage was caused by or contributed to by an act or omission,

(iii)  that the act or omission was that of the person against whom the claim is made, and

(iv)  that, having regard to the nature of the injury, loss or damage, a proceeding would be an appropriate means to seek to remedy it; and

(b)  the day on which a reasonable person with the abilities and in the circumstances of the person with the claim first ought to have known of the matters referred to in clause (a).

Section 5(2) adds a presumption that you discovered your claim the day the loss happened unless you can prove otherwise:

5(2) A person with a claim shall be presumed to have known of the matters referred to in clause (1) (a) on the day the act or omission on which the claim is based took place, unless the contrary is proved.

And section 15 sets the 15-year ultimate bar:

15 (1) Even if the limitation period established by any other section of this Act in respect of a claim has not expired, no proceeding shall be commenced in respect of the claim after the expiry of a limitation period established by this section.

In motor-vehicle cases, you also live under the Insurance Act^[2] and its threshold regime for non-pecuniary damages, with the evidentiary test spelled out in O. Reg. 461/96^[3].

Those statutes matter because a tort “pain and suffering” claim is not viable unless the injury crosses the serious-and-permanent threshold, which is often unknowable on day one.

The Core Principle: Discoverability Applies to Threshold Injuries

The Supreme Court settled the big point in Peixeiro v. Haberman, 1997 CanLII 325 (SCC)^[4]. A soft-tissue back case later revealed as a herniated disc turned on whether the limitation ran from the crash date or when the plaintiff first knew the injury was serious and potentially permanent. The Court held the discoverability rule applies. The limitation period doesn’t run until the plaintiff knew or ought to have known the material facts that make the claim viable — including that the injury crosses the statutory threshold. You don’t need the exact dollar value or a final prognosis, but you do need enough knowledge that a real claim exists.

What Counts as “Enough Knowledge”?

Canada’s top court later gave a clean formulation that Ontario courts have embraced across contexts.

A claim is discovered when you have the material facts upon which a plausible inference of liability can be drawn. You don’t need every element tied down or every expert report in hand. That standard — plausibility, not perfection — comes from Grant Thornton LLP v. New Brunswick, 2021 SCC 31^[5]. I wrote a blog on that case this past summer, “Tick…Tock…Time’s Up: Grant Thornton and the Limitation Period Time Bomb”^[6].

In the motor-vehicle sphere, translate that to this: once your client knows facts making it reasonably clear the injury is serious and likely permanent, and that someone’s fault caused it, the clock is running.

Due Diligence Helps, But It’s Not the Whole Test

The Ontario Court of Appeal has cautioned against turning “due diligence” into a standalone hurdle.

In Fennell v. Deol, 2016 ONCA 24^[7], an MVA plaintiff added a defendant after two years and the limitation issue turned on when he knew (or ought to have known) that his injuries were permanent and serious. The Court held the section 5(2) presumption can be rebutted by showing that, on the accident date, the plaintiff did not know the injury met the threshold. In other words, lack of diligence isn’t, by itself, a silver bullet for a limitation defence. The real question is when a reasonable person, with the plaintiff’s abilities and circumstances, actually would have known the claim met the threshold.

The Threshold’s Evidence Problem (and How Courts Treat It)

Trial courts have recognized the practical bind plaintiffs face in threshold cases It often takes months, sometimes longer, to obtain medical evidence capable of establishing a permanent serious impairment.

In Farhat v. Monteanu, 2015 ONSC 2119^[8], Perell J. accepted that a plaintiff cannot be expected to sue before there’s a reasonable basis, rooted in medical evidence, to believe the threshold can be met. The point isn’t that you can sit on your hands. It’s that the law does not force premature litigation before you can credibly plead past the threshold.

Another Appellate Anchor

The Court of Appeal has reiterated that discoverability turns on when the plaintiff knew or ought to have known the material facts, not when they obtained perfect proof.

In Everding v. Skrijel, 2010 ONCA 437^[9], the Court emphasized that a plaintiff doesn’t need to know the precise legal characterization or have conclusive reports. It’s enough that the facts support the inference a viable claim exists. That principle dovetails with threshold litigation, where the question is when the plaintiff could reasonably know they have a threshold-worthy injury.

How the Pieces Fit Together in the “Two-Years-Late Walk-In” Scenario

When a client pops into a lawyer’s office two years after the accident with what now looks like a chronic, life-altering injury, the limitation analysis is not a calendar count from the collision date. It is a discoverability analysis under section 5 of the Limitations Act, read in light of the Insurance Act threshold.

You must ask when did the client actually know, or when should they reasonably have known, that:

(1) a loss/injury occurred,

(2) it was caused by the defendant’s fault, and;

(3) given the seriousness and permanence of the impairment, a court proceeding was an appropriate means to seek a remedy?

If the best, objectively supportable answer post-dates the crash (for example, when a specialist first documents permanence or when function hasn’t improved despite reasonable treatment) the two-year period runs from that point.

What Evidence Moves the Needle

Courts expect real evidence that explains when the threshold became reasonably knowable.

In practice for both plaintiffs’ and defence counsel, that means charting the medical trajectory. Highlight not just pain complaints, but treatment response, objective or consistent clinical findings, functional impact that doesn’t resolve, and an expert’s permanence opinion when available. And tie these to dates. The record should show when the picture shifted from “might get better” to “likely permanent serious impairment.” That is what rebuts the section 5(2) presumption and aligns the file with Peixeiro, Fennell, Farhat, and the Grant Thornton plausibility standard.

Brass Tacks for Pleadings and Motion Records

If you’re defending a late-start negligence action, attack discoverability with the section 5(2) presumption and any contemporaneous documents suggesting early knowledge of permanence (e.g., client statements, insurer forms, treating notes).

If you’re acting for the plaintiff, lay out a dated medical narrative explaining when permanence came into responsible focus and why earlier discovery wasn’t reasonable. Avoid overclaiming. Courts don’t reward wishful thinking, they reward a credible timeline.

The appellate law does not let plaintiffs hide behind inertia, and it does not let defendants use “due diligence” as a magic eraser. It asks for a grounded, time-stamped evidentiary story as in Fennell.

Don’t Forget the Deductible/Threshold Administration Details

Because non-pecuniary damages in auto cases sit under s. 267.5^[10]and O. Reg. 461/96^[11], keep an eye on the indexed monetary threshold and deductible in the relevant year. Those numbers don’t control discoverability, but they matter to viability and settlement leverage. FSRA^[12] publishes the yearly figures^[13] Make sure the record reflects the correct year’s amounts when you assess “appropriateness” of suing.

The Three-Year Proposal: A Possible Reset of the Clock

Ontario’s Civil Rules Review Working Group has proposed extending the basic limitation period from two years to three, as part of the Phase 2 consultation paper^[14] under the province’s ongoing civil justice modernization initiative. The aim is to reduce premature filings and better align limitation law with the real-world timelines of medical recovery and expert evidence. For serious-injury cases, particularly those where the prognosis unfolds slowly, a three-year window could help bridge the gap between the patient’s lived recovery and the system’s procedural deadlines.

Still, until any legislative change arrives, counsel and mediators alike must continue to treat discoverability as both an art and a deadline-driven science. Whether the basic limitation remains two years or becomes three, the underlying race doesn’t change. It’s about when the clock truly starts to run.

Ready, Set, Go

In MVA threshold cases, the race doesn’t start at the moment of impact. It starts when the serious-and-permanent reality becomes reasonably knowable. That’s the true starting gun. Build or attack that moment with evidence, not rhetoric. The statute sets the clock, but Peixeiro and Grant Thornton define when the pistol fires. And as Fennell, Farhat, and Everding show, Ontario courts decide who jumped early, who waited too long, and who timed their start just right.

That’s the playbook.

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