Duty to mitigate refers to the obligation on a party who has suffered loss (typically following a breach of contract or tort/delict) to take reasonable steps to reduce that loss, rather than allowing it to accumulate. A claimant cannot recover damages for losses that could reasonably have been avoided.In England and Wales and Northern Ireland, the duty to mitigate is a common law principle developed through case law, especially in contract and tort. In Ireland and Scotland, the concept is similar, with Scottish law treating it as part of the rules on remoteness and quantification of damages in delict and contract. Across all four jurisdictions, the test is one of reasonableness, judged at the time of the alleged mitigation steps, not with hindsight.The duty does not require a claimant to take undue risk, incur disproportionate expense, or sacrifice substantial legal rights. A failure to mitigate does not extinguish the claim but limits recoverable damages to the loss that would have been suffered had reasonable mitigation occurred. The concept is routinely applied in commercial litigation, employment disputes, property damage claims and personal injury cases.