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Reasonable Mitigation Obligations:
Involves Duty to Avoid Unnecessary Losses or Damages
Last Updated: April 01 2026
Question: What does the duty to mitigate mean in Ontario, and what effort standard applies when claiming damages?
Answer: In Ontario civil claims, the duty to mitigate means you must take reasonable steps to reduce avoidable losses, and damages can be reduced for losses caused by your own inaction rather than the other party’s wrongdoing. Hall Paralegal Services provides paralegal services in Ontario to help assess mitigation steps, document your efforts, and present or defend mitigation arguments in Small Claims Court and related disputes, consistent with Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675.
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, the duty to mitigate requires a harmed person to minimize the harm suffered. Failure to minimize the harm may, and likely will, reduce the sum that the wrongdoer will owe the harmed person in a determination of liability at a court Trial. As was explained above by the Supreme Court in the Southcott Estates case, where a failure to mitigate occurs, it is the failure of the Plaintiff to act reasonably to minimize the loss that caused a portion of the harm. The wrongdoer is liable only for the portion of harm caused by the wrongdoer. Examples of mitigation include, among other things, the reasonable efforts of a wrongfully dismissed employee to seek fresh employment or for the victim of an injury to attend rehabilitation rather than to allow injuries to fester while loss of income for time off work accrues needlessly.
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 considerable quantity of online searches featuring “lawyers close to me” or “top lawyer in” typically indicate an urgent requirement for effective legal representation rather than pointing to a particular professional designation. In , licensed paralegals are governed by the same Law Society that supervises lawyers and are permitted to represent clients in specific litigation matters. Advocacy, legal analysis, and procedural expertise are fundamental to that function. Hall Paralegal Services provides legal representation within its licensed parameters, focusing on strategic positioning, evidentiary preparation, and compelling advocacy aimed at securing efficient and favourable outcomes for clients.