Last Updated: August 22 2026
How does the duty to mitigate losses affect damages in an Ontario civil lawsuit?
In Ontario civil disputes, the duty to mitigate means a harmed party must take reasonable steps to reduce or control losses caused by the other side’s breach or wrongdoing, so you generally can’t recover amounts that could reasonably have been avoided through timely action, as explained by Southcott Estates Inc. v. Toronto Catholic District School Board, [2012] 2 S.C.R. 675, and the defendant bears the burden to prove both a failure to make reasonable efforts and that mitigation was possible. Reasonable mitigation does not require perfection; it requires proportionate, timely actions as circumstances unfold, and in some cases you may recover reasonable costs incurred to mitigate (including certain expenses tied to those efforts). If you want help assessing whether your conduct was reasonable and how to address (or respond to) a mitigation defence in your pleadings, Civil Litigations Paralegal Services (Ontario) can guide you at (416) 229-1479.
Add this website to Google Preferred Sources
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.
Note: Please contact Civil Litigations Paralegal Services by phone at: (416) 229-1479 to discuss any specific questions that you may have.
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, 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. 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.
NOTE: A significant array of queries like “lawyers near me” or “best lawyer in” frequently indicates a desire for prompt and effective legal support as opposed to a particular designation. In Ontario, paralegals who hold a license are governed by the same Law Society that regulates lawyers and are empowered to represent clients in specific litigation areas. The core elements of this role include advocacy, legal insight, and procedural expertise. Civil Litigations Paralegal Services provides legal representation within its licensed parameters, focusing on strategic alignment, evidence preparation, and compelling advocacy aimed at securing swift and positive outcomes for clients.
