A quasi-contract is also known as an ‘implied in law contract’ or a ‘constructive contract’ and is not actually a contract at all, despite being recognised as such by a court. Quasi-contracts can be traced back to Roman law, and attempted to remedy what is now known as unjust enrichment.

The term is sometimes used to cover extra-contractual remedies such as money had and received and quantum meruit, instead of the more appropriate term restitution, which does not invoke any fictional contract.