Khan v. Taji confirms that common law discovery applies to the limitation period in s. 4 of the Real Property Limitations Act. It provides a good overview of the issue:
[72] The defendants argue that the discoverability principle in s. 5 of the Limitations Act, 2002, has no application to s. 4 of the RPLA. They argue that the discoverability principle is a statutory construct, and does not apply unless expressly stated in the statute. In the absence of an express statement, the right to bring an action for the recovery of land first accrues the moment the trust is established, not on the date that a breach of trust is discovered.
[73] There is no question that the application of the discoverability rule is a question of statutory interpretation, but the analysis is not as simple as that proposed by the defendants. In Pexeiro v. Haberman, 1997 CanLII 325 (SCC), [1997] 3 S.C.R. 549 (S.C.C.), the Supreme Court of Canada dealt with the question of whether the discoverability rule applied to all limitation provisions or whether its application depended upon the actual wording of the statutory limitation. Major J. adopted the following statement from the Manitoba Court of Appeal in Fehr v. Jacob , at para. 37:
[T]he judge-made discoverability rule is nothing more than a rule of construction. Whenever a statute requires an action to be commenced within a specified time from the happening of a specific event, the statutory language must be construed. When time runs from “the accrual of the cause of action” or from some other event which can be construed as occurring only when the injured party has knowledge of the injury sustained, the judge-made discoverability rule applies. But, when time runs from an event which clearly occurs without regard to the injured party’s knowledge, the judge-made discoverability rule may not extend the period the legislature has prescribed. (Emphasis added)
[74] In McCracken v. Kossar, 2007 CanLII 4875 (ON SC), Shaw J. concluded that the language of s. 4(1) of the RPLA did nor preclude the application of the discoverability rule, at para. 54:
Ms. Kossar submits that the discoverability principle does not apply to s. 4(1) of the Real Property Limitations Act. She quotes in support of her submission the words in s. 4(1), “… when the right to bring such action first accrued.” However, Fehr v. Jacob, cited with approval by Major J. in Pexeiro, refers to very similar language as leading to the possible application of the discoverability rule.
[75] In any event, I note that s. 28 of the RPLA does expressly provide for a discoverability rule in cases of concealed fraud. Section 28 provides:
28. In every case of a concealed fraud, the right of a person to bring an action for the recovery of any land or rent of which the person or any person through whom that person claims may have been deprived by the fraud shall be deemed to have first accrued at and not before the time at which the fraud was or with reasonable diligence might have been first known or discovered.