Both express contracts and implied contracts are legally enforceable promises of mutual assent to be bound, see U.C.C. § 1-201. An express contract is communicated orally or in writing, which requires expressing assent. An implied contract, which does not have explicitly stated terms, is still found to exist because parties assumed a contract existed based on conduct, or denying the contract's existence would result in unjust enrichment to one of the parties. An implied contract is divided into Implied-in-fact contract and Implied-in-law contract.
An implied-in-fact contract is formed when parties’ promises are inferred from their intentional conduct and one party knows or at least has reason to know the other party will interpret the conduct as assent or an agreement. For instance, if a customer accepts services from a merchant or gets products from that merchant, then they should pay for the reasonable value of services or products (e.g., barbershop, vending machine). However, under some circumstances, even if a defendant has received nothing of value, the implied-in-fact contract can still be enforced.
Implied-in-law contract (Quasi contract)
An implied-in-law contract is the restitution recovery at law, which imposes a legal obligation to an unjustly enriched party to compensate the other party. It is not only applied when there is no contract but also applied when there is a total breach of contract. There are no requirements for the meeting of the minds or mutual assent. Once the plaintiff has conferred a measurable benefit on the defendant without gratuitous intent and the defendant gets the unjust enrichment, the court will imply a quasi contract as a method of recovery. The measure of recovery is not the contract price, but the reasonable fair value of the benefit conferred.
Unjust enrichment or unfairness arises when the defendant has the opportunity to decline the benefit but instead knowingly accepts it. However, if the plaintiff has an excuse for not giving the defendant such an opportunity (e.g., rescuing someone in an emergency), he or she also has the right of claiming remedy.
Instead of being governed by contract law, the implied-in-law contract is governed by equitable relief.
Compare: express contract
[Last updated in March of 2022 by the Wex Definitions Team]