An injured party may not recover damages it could have avoided by reasonable effort without undue risk, burden or humiliation. It is not truly a duty — no one is sued for failing to mitigate — but a limit on recovery.

The burden is on the breaching party to prove that reasonable steps existed and were not taken, and to prove what they would have saved. That allocation matters: a vague assertion that the plaintiff should have done better fails.

Reasonableness is judged as of the time, not with hindsight. A claimant who chooses a reasonable course that turns out badly is still protected. One who does nothing at all rarely is.

Common applications. A wrongfully terminated employee must look for comparable work, though not lesser or distant work. A seller of rejected goods must attempt resale. A landlord in most states must attempt to re-let. A buyer denied delivery must consider cover.

Costs of mitigating are recoverable, including where the attempt fails, so long as the attempt was reasonable. That is important: mitigation does not shift the expense onto the victim.

Evidence discipline. Keep the record of the effort — applications sent, brokers engaged, quotes obtained, dates. Mitigation is proved with documents, and the party that kept them contemporaneously is far better placed than the one reconstructing a search two years later.