Definition
A quasi contract is a legal obligation imposed by courts on a party who has received a benefit from another, where no actual contract exists but allowing the recipient to keep the benefit without paying for it would be unjust. The court treats the parties as if they had contracted, not because they did, but because fairness demands it.
Quasi contract is not a true contract. It is a remedy-generating fiction: courts impose a contractual-style obligation to prevent unjust enrichment. The parties need not have agreed to anything, and there need not have been any meeting of the minds. The obligation arises from law, not from consent.
In modern usage, quasi contract is the doctrinal ancestor of the law of unjust enrichment and restitution. The two concepts substantially overlap, and in many jurisdictions quasi contract has been functionally absorbed into restitution doctrine, though the older label persists in case law and pleading.
Common Confusion
Quasi contract is frequently conflated with implied-in-fact contract, but the two are legally distinct. An implied-in-fact contract is a real contract — one whose terms are inferred from the conduct of the parties rather than their words. Both parties have consented; the agreement is simply unspoken. A quasi contract involves no consent at all. The obligation is imposed entirely by law to prevent unjust enrichment. The confusion is compounded because courts and older treatises sometimes use "implied contract" loosely to cover both categories. Researchers encountering "implied contract" in historical sources must determine from context which kind is meant.
Quasi contract should also be distinguished from contracts implied in law, a phrase used as a synonym for quasi contract in many older authorities. Modern courts generally reserve "implied-in-law contract" for what is now more precisely called quasi contract or restitution.
Core Elements
To recover on a quasi contract theory, the plaintiff typically must show:
1. A benefit was conferred on the defendant by the plaintiff.
2. The defendant had knowledge of, or appreciated, the benefit.
3. Acceptance or retention of the benefit under circumstances making it inequitable to do so without compensation.
These elements track the modern unjust enrichment framework. Some jurisdictions add a fourth element requiring that no adequate remedy exists at law, though this requirement has receded as restitution doctrine has matured.
Why It Matters in Research
Researchers face a layered terminological problem with quasi contract. In civil law sources and older common law texts, quasi contract is a substantive category of obligation sitting alongside contract, tort, and delict. In modern American and English law, the same ground is largely covered by unjust enrichment and restitution doctrine, and quasi contract survives mainly as a pleading vehicle or historical label.
When searching historical case law — particularly pre-twentieth century — researchers should expect quasi contract to appear as a stand-alone cause of action. In modern materials, the same claim is more likely styled as unjust enrichment, restitution, or quantum meruit. These are not different claims so much as different vocabularies for the same underlying theory.
Quantum meruit and quantum valebant are the most common quasi-contractual remedies in the corpus and deserve separate attention. Researchers tracing a quasi contract claim should pull those entries as well as any implied contract authority in the relevant jurisdiction.
The civil law pedigree of quasi contract matters for interpretation. The historical dictionaries reflect a Roman law taxonomy — obligationes quasi ex contractu — that shaped how English and American courts originally imported the concept. That lineage explains why civil law sources such as the Digest and civilian commentators appear in common law quasi contract opinions well into the nineteenth century.
Jurisdictional variation is significant in one important respect: some states have largely replaced quasi contract pleading with statutory or code-based restitution frameworks, while others retain quasi contract as a recognized independent cause of action. Corpus searches limited to one state's materials may not generalize.
Historical Dictionary Support
Black's Law Dictionary defines quasi contract as a "contractual relation arising out of transactions between the parties which give them mutual rights and obligations, but do not involve a specific and express convention or agreement." Black's correctly locates the concept in civil law and identifies it as a species of implied contract, though the phrase "species of implied contract" papers over the implied-in-fact versus implied-in-law distinction that modern doctrine treats as critical.
Burrill's Law Dictionary is more precise on the civil law origin and more candid about the fiction involved, describing quasi contract as an "improper contract" and noting that the obligation was "founded on the consent of the parties, not actually expressed, but implied or presumed by law." Burrill's citation to Heineccius (Elementa Juris Civilis) reflects the direct civilian lineage of the concept. Burrill also signals that quasi contract was an "intermediate head" for obligations that could not comfortably fit elsewhere — an important caution for researchers: the category historically served as a doctrinal catch-all, and the cases gathered under it are not always analytically coherent.
Neither historical dictionary adequately addresses the modern transformation of the doctrine. Both treat quasi contract as a self-contained category rather than anticipating its near-merger with unjust enrichment. Researchers should not rely on either dictionary to characterize the state of quasi contract doctrine after the mid-twentieth century.
Jurisdictional Note
American jurisdictions vary in whether they treat quasi contract as a distinct cause of action or simply as a label for unjust enrichment claims. Louisiana, as a mixed civil law jurisdiction, retains doctrinal frameworks closer to the original civilian structure. In most common law states, quasi contract and unjust enrichment are functionally interchangeable, though pleading forms differ.
Encyclopedia Cross-Reference
Contracts — Classification (Bilateral, Unilateral, Express, Implied, Quasi-Contract), The Law Mind Contracts & Commercial Law Encyclopedia