A quasi-contract (or implied-in-law contract or constructive contract) is a fictional contract recognised by a court. The notion of a quasi-contract can be traced to Roman law and is still a concept used in some modern legal systems. Quasi Contract laws have got deduced from the Latin statement “Nemo debet locupletari ex aliena jactura”, which proclaims that no man should grow rich out of another person’s loss. It was one of the central doctrines of Roman law. The word Quasi means having some similarities but not entirely. Similarly, such a Contract means laws like ordinary contract law but not totally.
In common law jurisdictions, the law of quasi-contract can be traced to the medieval form of action known as indebitatus assumpsit. In essence, the plaintiff would recover a money sum from the defendant as if the defendant had promised to pay it: that is, as if there were a contract subsisting between the parties. The defendant's promise—their agreement to be bound by the "contract"—was implied by law. The law of quasi-contract was generally used to enforce restitutionary obligations.
The form of action known as indebitatus assumpsit came to include various sub-forms known as the common money counts. The most important of these for the later development of the law of quasi-contract included: (i) actions for money had and received to the plaintiff's use; (ii) actions for money paid to the defendant's use; (iii) quantum meruit; and (iv) quantum valebant.
Quasi-contractual actions were generally (but not exclusively) used to remedy what would now be called unjust enrichment. In most common law jurisdictions the law of quasi-contract has been superseded by the law of unjust enrichment. Under section 69 of the Indian contract act of 1872, there are six types of Quasi-contract laws.
A quasi-contract is distinct from a contract implied in fact and may be distinguished from an explicitly agreed contract.[a] The main difference between a Contract and Quasi Contract is that there is no exchange of offer, acceptance, or consideration between two or more parties in the latter's case. However, it is still legally enforceable.