In Ontario, in many cases the basic limitation period, pursuant to the Limitations Act, 2002 (S.O. 2002, c. 24, Sch. B, section 4) to commence a lawsuit is two years from the date of loss. The limitation date applies irregardless of the Court before which you are bringing the Claim (i.e. Small Claims Court, or Superior Court of Justice). Limitation dates also apply to proceedings brought under Administrative Tribunals such as the Human Rights Tribunal of Ontario (where an Application must be brought within one year). The limitation date is extremely important because if you miss it, you cannot take steps after that point to advance a claim: you’re out of luck.
But what if you did not know that someone else’s negligent actions were in fact an actionable wrong resulting in injury or other damages, until a later date? Here raises the issue of discoverability. Natural justice suggests that you cannot be barred from pursuing legal action against someone when you do not yet even know they are responsible for the damages suffered. The Supreme Court of Canada (Peixeiro v. Haberman  3 S.C.R. 549, para 18) has identified this actionable wrong, or cause of action, stating:
Once the plaintiff knows that some damage has occurred and has identified the tortfeasor… the cause of action has accrued.
Therefore, the injured party must identify that damage has occurred, and that the person (or other entity) is responsible for those damages. On the date that that occurs, the limitation period is triggered, and the limitation clock starts ticking.
The injured party does bear some responsibility for taking steps to discover the cause of action where such steps would be reasonable. Justice Morden, for the Court of Appeal in Johnson et al. v. Wunderlich et al. ( O.J. No. 1251, 57 O.R. (2d) 600, at para 18), explained discoverability:
The cause of action accrues when the plaintiff (the person insured) has discovered these material facts or ought to have discovered them by the exercise of reasonable diligence.
Similarly, at the Ontario Court of Appeal, Justice MacKinnon writes in July v. Neal (57 O.R. (2d) 129, 32 D.L.R. (4th) 463 at page 7) that:
… the time begins to run under such circumstances as the instant case, when the material facts on which the claim is based have been discovered or ought to have been discovered by the plaintiff by the exercise of reasonable diligence.
In other cases, there is, in fact, no cause of action until any damages reach a sufficient level of seriousness to support a claim, such as in Ontario motor vehicle accident litigation where a statutory threshold of seriousness must be met. The Supreme Court held in Peixeiro v. Haberman, supra, at para 30, “No cause of action exists until sufficient severity of injury exists.” In some circumstances, this could raise an exception to the Limitation rule. Nevertheless, it would not be advisable to miss a limitation date when the date of loss is reasonably known because of the serious and possibly irreparable consequences for doing so.
If you are unsure about the Limitation date in your circumstances and are concerned about missing it, do not delay. Contact a lawyer to assist you with the particulars of your case.