A quasi-contract (or implied-in-law contract or constructive contract) is a fictional contract created by courts for equitable, not contractual, purposes. A quasi-contract is not an actual contract, but is a legal substitute formed to impose equity between two parties. The concept of a quasi-contract is that of a contract that should have been formed, even though in actuality it was not. It is used when a court finds it appropriate to create an obligation upon a non-contracting party to avoid injustice and to ensure fairness. It is invoked in circumstances of and is connected with the concept of restitution.