Unlike a Breach of Contract case — which, as you can surely guess, requires the existence of an enforceable contract — a restitution/unjust enrichment claim does not require a contract.
Unjust enrichment occurs legally when one person/entity is unfairly enriched at the expense of another, thereby creating an obligation to compensate the other for the benefit provided. As an example, say I build a fence on what I believe is my property. It later turns out that it was in fact on my neighbor’s property. My neighbor’s property value goes up as a result of the fence. There is a strong chance that I could go into court and say that I should be compensated for my good faith work which enhanced my neighbor’s property value.
Under Missouri Law, there are four elements that need to be proven to prevail on a restitution action:
(1) A party conferring benefits on another party in good faith;
(2) The party receiving the benefit actually benefited;
(3) Retention of the benefits would be unequitable; and
(4) There is no adequate remedy at law.