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 Minnesota, 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 doctrine applies when one party makes a promise that the other party relies upon to their detriment. For promissory estoppel to be invoked in Minnesota, the following elements must typically be present: a clear and definite promise, the promisee's reliance on the promise to their detriment, the reliance was reasonable and foreseeable, and injustice can only be avoided by enforcing the promise. Minnesota courts will consider these factors to determine if it is equitable to hold the promisor to their promise, even without the traditional consideration that a contract usually requires. Detrimental reliance is not considered a separate tort but rather a principle of fairness within contract law to prevent unjust outcomes.