Promissory estoppel is an equitable theory of recovery that permits enforcement of a promise when one or more elements necessary to create an enforceable contract are missing. The elements of promissory estoppel are generally: (1) a promise; (2) foreseeability of reliance by the promisor; (3) substantial and reasonable reliance by the promisee to its detriment; and (4) enforcing the promise is necessary to avoid injustice.

In Colorado, promissory estoppel serves as a legal remedy that allows a party to enforce a promise even when a formal contract does not exist or certain elements for a contract are lacking. The doctrine is based on the principle of fairness and seeks to prevent injustice that would result from not enforcing the promise. The elements required for promissory estoppel in Colorado are: (1) the presence of a promise that is expected to induce action or forbearance, (2) the promise must be one that the promisor could reasonably expect to induce action or forbearance by the promisee, (3) actual and reasonable reliance on the promise by the promisee to their detriment, and (4) the necessity of enforcing the promise to avoid an injustice. If these elements are met, Colorado courts may enforce the promise as if it were a contract, even in the absence of a formal agreement. This doctrine is particularly relevant in situations where parties have acted on promises that are not supported by consideration, which is typically required for a contract to be enforceable.