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Reasonable Mitigation Obligations:
Involves Duty to Avoid Unnecessary Losses or Damages
Last Updated: June 11 2026
Question: What is the duty to mitigate in Ontario, and what “reasonable efforts” do I need to make to avoid reducing my claim?
Answer: In Ontario, the duty to mitigate means you must take reasonable steps to minimize your losses after a breach, injury, or other wrong, and you generally can’t claim damages that could reasonably have been avoided; for clarity, Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675 confirms the standard is reasonable efforts, not perfection, and the other side must prove both a failure to mitigate and that mitigation was possible. For practical, affordable Paralegal Services across Ontario, Woodcock Legal Services can help you document mitigation steps, respond to mitigation arguments, and protect the value of your claim, so call (613) 334-6721 to get started.
The Duty to Mitigate Including the Standard of Efforts to Do So
The law despises waste and the doctrine of mitigation, being the duty to mitigate, is the mechanism that imposes an obligation upon a harmed party to take reasonable steps to minimize or control avoidable losses. This doctrine in law requiring efforts to mitigate applies to all matters of law including tort law, contract law, employment law, construction law, among other legal issues.
The Law
The duty to mitigate was articulated well by the Supreme Court within the case of Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675, where it was said that:
[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. When a Defendant to a lawsuit seeks to argue failure to mitigate as a defence strategy, the Defendant must include such an allegation with the defence pleading documents and it is the Defendant that must prove that the Plaintiff had a reasonable opportunity to mitigate the losses and failed to do so. However, the Plaintiff is without a requirement to mitigate perfectly and must only take such steps that are reasonable at the time that the loss is occurring rather than as may appear possible at a later date through hindsight.
NOTE: A large number of online searches for “lawyers nearby” or “top lawyer in” frequently indicate a desire for prompt and effective legal support rather than a specific professional designation. In Ontario, licensed paralegals are governed by the same Law Society that regulates lawyers, granting them the authority to represent clients in specific litigation areas. Key elements of this role include advocacy, legal assessment, and procedural expertise. Woodcock Legal Services provides legal representation within its licensed framework, focusing on strategic planning, evidence preparation, and compelling advocacy, all aimed at attaining swift and advantageous outcomes for clients.
