When parties to a contract make promises to perform their obligations, and one party reasonably relies on the other party’s promise—but the party making the promise fails to perform, causing harm or loss to the party who relied on the promise—the party who relied on the promise to perform is said to have relied to its detriment.

This legal concept is called detrimental reliance. Detrimental reliance may serve as a substitute for consideration, and make an otherwise unenforceable contract enforceable.

Thus, detrimental reliance is a legal concept based on fairness (known as equity or equitable), and is equivalent to contractual promissory estoppel (due to the other party’s reliance, the party who did not keep its promise is prohibited from challenging the enforceability of its promise).

Detrimental reliance is not a separate tort cause of action.

In Louisiana, the concept of detrimental reliance is recognized and is similar to the doctrine of promissory estoppel found in other jurisdictions. Under Louisiana law, when one party to a contract makes a promise that the other party relies on to their detriment, this reliance can make an otherwise unenforceable agreement enforceable. This principle is rooted in the notions of fairness and equity, ensuring that a party who has made a promise cannot argue against the enforceability of that promise if the other party has suffered a loss due to their reliance on it. Detrimental reliance in Louisiana serves as a means to uphold the obligations of a party in a contractual relationship, even in the absence of formal consideration, provided that the reliance was reasonable and the resulting harm can be demonstrated. It is important to note that detrimental reliance is not considered a separate cause of action in tort, but rather a legal theory that can affect the enforcement of contracts.