What is unjust enrichment and can I use it in a contract dispute in Ontario?

Unjust enrichment is an equitable claim that arises when one party is enriched at the expense of another, with no juristic reason — no valid legal basis — for keeping the benefit. It exists alongside, and sometimes as an alternative to, breach of contract claims.

In Ontario, to succeed in unjust enrichment you must show: the defendant was enriched, the enrichment came at your expense, and there is no juristic reason for the defendant to keep the benefit. A valid, enforceable contract between the parties is itself a juristic reason, which is why unjust enrichment often comes into play where there is no enforceable contract — for example, if a contract is void, unenforceable, or never fully formed.

The remedy for unjust enrichment is typically restitution — returning the value of the benefit — rather than expectation damages. Courts may award a money sum or, in some property cases, a constructive trust.

Unjust enrichment claims arise in family property disputes, failed business ventures, and situations where services or money were provided under a contract that turned out to be invalid. If you paid for something under a contract that is later found unenforceable, an unjust enrichment claim may let you recover what you paid even if you cannot recover your expected profit.