An obligation imposed by law to prevent unjust enrichment. Also called a contract implied in law or a constructive contract, a quasi contract may be presumed by a court in the absence of a true contract, but not where a contract—either express or implied in fact—covering the same subject matter already exists.
Because a quasi contract is not a true contract, mutual assent is not necessary, and a court may impose an obligation without regard to the intent of the parties. When a party sues for damages under a quasi-contract, the remedy is typically restitution or recovery under a theory of quantum meruit. Liability is determined on a case-by-case basis.