Singh v. Trump, 2016 ONCA 747:
 This court has consistently held that "[t]he expiry of a limitation period is a defence to an action that must be pleaded in a statement of defence": Collins v. Cortez, 2014 ONCA 685,  O.J. No. 4753, at para. 10, per van Rensburg J.A. (citing S. (W.E.) v. P. (M.M.) (2000), 50 O.R. (3d) 70 (C.A.), at paras. 37-38, leave to appeal to S.C.C. refused,  149 O.A.C. 397). This requirement is embodied in rule 25.07(4) of the Rules of Civil Procedure, which Ontario courts have consistently held "applies to pleadings relating to limitations that might bar an action": S. (W.E.) v. P. (M.M.), at para. 37. Rule 25.07(4) provides as follows:
In a defence, a party shall plead any matter on which the party intends to rely to defeat the claim of the opposite party and which, if not specifically pleaded, might take the opposite party by surprise or raise an issue that has not been raised in the opposite party's pleading.
 Justice Cronk explained the rationale behind the requirement that a party specifically plead a limitation period defence in Hav-A-Kar Leasing Ltd. v. Vekselshtein, 2012 ONCA 826, 225 A.C.W.S. (3d) 237, at para. 69:
The failure to raise substantive responses to a plaintiff's claims until trial or, worse, until the close of trial, is contrary to the spirit and requirements of the Rules of Civil Procedure and the goal of fair contest that underlies those Rules. Such a failure also undermines the important principle that the parties to a civil lawsuit are entitled to have their differences resolved on the basis of the issues joined in the pleadings.
 In S. (W.E.) v. P. (M.M.), MacPherson J.A. confirmed that Ontario courts "have consistently held that rule 25.07(4) applies to pleadings relating to limitations that might bar an action": at para. 37. He went on to explain that even though in that case the trial judge had given counsel time to prepare submissions on the issue after he raised it during closing arguments, it did not remove the potential prejudice to P:
If S had raised the issue in his pleadings, P might have tried to settle, or even have abandoned, her counterclaim. Either decision might have had costs consequences. Another potential source of prejudice arises from the fact that counsel for P might have adopted different tactics at trial. In particular, counsel might have called different or additional evidence to support an argument that the discoverability principle applied (at para. 38).