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 Tennessee, the legal concept of detrimental reliance, also known as promissory estoppel, is recognized and can be used to enforce a contract that may otherwise lack consideration and be unenforceable. This principle applies when one party makes a promise that the other party relies on to their detriment. If the promisor fails to fulfill their promise, and the promisee has reasonably relied on that promise to their harm, the promisee may invoke detrimental reliance to enforce the promise. Tennessee courts will consider factors such as the reasonableness of the promisee's reliance and the extent of the detriment suffered. Detrimental reliance is grounded in principles of fairness and equity, aiming to prevent injustice by prohibiting the promisor from arguing against the enforceability of the promise. It is important to note that detrimental reliance is not an independent tort claim but rather a doctrine that can affect the enforceability of contractual obligations.