A person who freely enjoys the benefit of a NON-GRATUITOUS ACT done by another, or of a thing delivered to him, must compensate that other person under the Indian Contract Act, 1872. This quasi-contractual obligation is embodied in:

Section 70 of the Indian Contract Act enacts a quasi-contract (now generally termed a claim in restitution/quantum meruit): where a person lawfully does anything for another person, or delivers anything to him, NOT intending to do so gratuitously, and the other person ENJOYS the benefit thereof, the latter must compensate the former, or restore the thing. It applies even in the absence of an enforceable contract, provided the act was done legally and not gratuitously and the benefit was accepted. Section 68 concerns necessaries supplied to a minor, Section 72 money paid by mistake/coercion, and Section 65 restitution on a void agreement or contract becoming void.