Last Updated: August 22 2026
If I was harmed by a breach in Ontario, what does the duty to mitigate require and how do I show I took reasonable steps?
In Ontario, the duty to mitigate means you must take all reasonable steps to minimize the losses flowing from the other party’s wrongdoing, and you may lose (or reduce) recovery for any harm that could reasonably have been avoided through your inaction. Southcott Estates Inc. v. Toronto Catholic District School Board, 2012 SCC 51, explains that mitigation bars the portion of damages caused by neglect to take reasonable steps, and it also emphasizes that damages incurred in genuinely mitigating can be recoverable if reasonable. If the other side alleges you failed to mitigate, they generally have the burden to prove both that reasonable mitigation efforts were not made and that mitigation was possible, while you are expected to act reasonably, not perfectly. Theresa Forrest, Paralegal helps Ontario clients assess what steps count as reasonable mitigation in their specific situation (like seeking employment after wrongful dismissal or pursuing rehab after injury) and how to document those efforts, call (519) 902-4223 to get started with a quick review.
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The Duty to Mitigate Including the Standard of Efforts to Do So
In a conscientious society, reasonably minded persons prefer to avoid waste; and accordingly, the law imposes the principle of mitigation, being a duty to mitigate, upon a harmed party. The duty to mitigate imposes a requirement upon a harmed person to act reasonably by taking steps that reduce or control losses and applies to all areas of law.
Note: For immediate help, please contact Theresa Forrest, Paralegal by phone at: (519) 902-4223 to retain services or to discuss any specific questions that you may have.
The Law
The Supreme Court very well explained the duty to mitigate within the case of Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675, whereas the court said:
[23] This Court in Asamera Oil Corp. v. Seal Oil & General Corp., 1978 CanLII 16 (SCC), [1979] 1 S.C.R. 633, cited (at pp. 660-61) with approval the statement of Viscount Haldane L.C. in British Westinghouse Electric and Manufacturing Co. v. Underground Electric Railways Company of London, Ltd., [1912] A.C. 673, at p. 689:
The fundamental basis is thus compensation for pecuniary loss naturally flowing from the breach; but this first principle is qualified by a second, which imposes on a plaintiff the duty of taking all reasonable steps to mitigate the loss consequent on the breach, and debars him from claiming any part of the damage which is due to his neglect to take such steps.
[24] In British Columbia v. Canadian Forest Products Ltd., 2004 SCC 38 (CanLII), [2004] 2 S.C.R. 74, at para. 176, this Court explained that “[l]osses that could reasonably have been avoided are, in effect, caused by the plaintiff’s inaction, rather than the defendant’s wrong.” As a general rule, a plaintiff will not be able to recover for those losses which he could have avoided by taking reasonable steps. Where it is alleged that the plaintiff has failed to mitigate, the burden of proof is on the defendant, who needs to prove both that the plaintiff has failed to make reasonable efforts to mitigate and that mitigation was possible (Red Deer College v. Michaels, 1975 CanLII 15 (SCC), [1976] 2 S.C.R. 324; Asamera; Evans v. Teamsters Local Union No. 31, 2008 SCC 20 (CanLII), [2008] 1 S.C.R. 661, at para. 30).
[25] On the other hand, a plaintiff who does take reasonable steps to mitigate loss may recover, as damages, the costs and expenses incurred in taking those reasonable steps, provided that the costs and expenses are reasonable and were truly incurred in mitigation of damages (see P. Bates, “Mitigation of Damages: A Matter of Commercial Common Sense” (1992), 13 Advocates’ Q. 273). The valuation of damages is therefore a balancing process: as the Federal Court of Appeal stated in Redpath Industries Ltd. v. Cisco (The), 1993 CanLII 3025 (FCA), [1994] 2 F.C. 279, at p. 302: “The Court must make sure that the victim is compensated for his loss; but it must at the same time make sure that the wrongdoer is not abused.” Mitigation is a doctrine based on fairness and common sense, which seeks to do justice between the parties in the particular circumstances of the case.
Accordingly, mitigation requires the minimizing of harm. Failure to minimize the harm is a failure to mitigate and may reduce sums that a wrongdoer owes to the person harmed whereas when a failure to mitigate occurs, it is the person who was harmed and failed to reasonably minimize loss that caused some of the harm. Simply said, where the Defendant does something wrong resulting in harm to the Plaintiff, the Defendant is responsible only for the portion of the harm that arises directly due to the wrongdoing of the Defendant and where a portion of the harm occurs or accrues because the Plaintiff failed to minimize that harm, the Plaintiff is at blame for the portion of the harm.
Conclusion
A Plaintiff (or Defendant within a counterclaim) is required to mitigate by taking reasonable steps to keep losses at a minimum. Where a Plaintiff fails to reasonably take steps to minimize losses, it is the inaction of the Plaintiff rather than the wrongdoing of the Defendant that caused such losses. Where failure to mitigate is alleged by the Defendant, it is the Defendant who holds the duty to prove that the Plaintiff failed to mitigate and that a reasonable opportunity to mitigate was available; furthermore, the duty upon the Plaintiff is to take reasonable steps in the effort to mitigate rather than take steps to perfectly mitigate and a Defendant is unable to use the vision of hindsight to argue what the possible opportunities to mitigate were available to the Plaintiff. Again, the duty is to act reasonably without expectations of perfection.
