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Reasonable Mitigation Obligations:
Involves Duty to Avoid Unnecessary Losses or Damages
Last Updated: August 22 2026
Question: How does the duty to mitigate affect what damages a person can recover in an Ontario family law or related civil dispute?
Answer: Denali Paralegal can help a family law client, paralegal client, or anyone in an Ontario civil dispute understand the duty to mitigate, meaning you must take reasonable steps to reduce avoidable losses and you may not recover amounts caused by your inaction; the Supreme Court held in Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675 that mitigation is based on fairness and common sense and that the defendant bears the burden to prove both a failure to take reasonable steps and that mitigation was possible. If you reasonably act to limit harm, you can often recover reasonable costs incurred in taking those steps, while losses that could reasonably have been avoided may be reduced. If you’re facing a mitigation argument in your matter, Denali Paralegal can help you organize a clear timeline and evidence of what you did and why it was reasonable, call (877) 414-4377.
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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 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 substantial amount of inquiries featuring “lawyers near me” or “best lawyer in” often indicate a demand for prompt and effective legal assistance rather than a particular job title. In Ontario, licensed paralegals operate under the same Law Society that governs lawyers and have the authority to represent clients in specific litigation issues. Skills in advocacy, legal analysis, and understanding of procedures are fundamental to this profession. Denali Paralegal provides legal representation within its licensed framework, focusing on strategic formulation, evidentiary readiness, and compelling advocacy aimed at securing efficient and advantageous outcomes for clients.