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Reasonable Mitigation Obligations:
Involves Duty to Avoid Unnecessary Losses or Damages
Last Updated: June 12 2026
Question: What is the duty to mitigate in Ontario civil claims, and what effort is considered “reasonable” to reduce your losses?
Answer: In Ontario, the duty to mitigate means you must take reasonable steps, as the loss occurs, to reduce your damages after a breach or wrongdoing, and you generally can’t recover losses you could have avoided; the leading guidance comes from Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675, which confirms reasonableness is judged in the circumstances and not with hindsight. For practical support documenting your efforts, gathering evidence, and preparing persuasive materials, Defend-it Legal Services provides Paralegal Services, Private Investigation, Background Searches & Fingerprinting Agency support across Ontario, so you can protect your claim’s value and move forward faster, call (289) 275-3513 now.
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. 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 doctrine of mitigation was explained well whereas it was said in general by the Supreme Court in Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675, 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
The law required that a Plaintiff (or a Defendant within a counterclaim against the Plaintiff) took reasonable steps to mitigate, meaning reduce, losses. When a person failed to take reasonable steps to mitigate (reduce losses), the law will disallow claims, or the amounts within claims, that arose because of the failure to mitigate whereas the law views the losses that arise from the failure to mitigate as caused by the inaction of the victim rather than by the action of the wrongdoer. 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 considerable amount of online inquiries featuring “lawyers close to me” or “top lawyer in” frequently indicate a demand for prompt and competent legal assistance instead of a particular job title. In Ontario, “licensed paralegals” are governed by the same Law Society that regulates lawyers, granting them the authority to represent clients in specific litigation scenarios. Advocacy, legal assessment, and procedural expertise are fundamental aspects of this position. Defend-it Legal Services provides legal representation within its licensed framework, focusing on strategic positioning, evidentiary preparation, and persuasive advocacy directed at attaining efficient and beneficial outcomes for clients.
