Promissory estoppel enforces a promise that lacks consideration where the promisor should reasonably have expected it to induce action or forbearance, it did, and injustice can be avoided only by enforcement.
The elements are a clear and definite promise, reasonable and foreseeable reliance, actual reliance, and resulting detriment. Courts insist on the first element more than litigants expect: expressions of optimism, projections and statements of present intention are not promises.
Reliance must be reasonable, which is a heavy lift where the parties are sophisticated, the negotiations expressly contemplate a written agreement, or a letter of intent says it is non-binding. A party told in writing that nothing is agreed until signature has a hard time claiming reasonable reliance.
Remedy. Courts frequently limit recovery to reliance damages — what was spent in reliance — rather than the full benefit of the bargain. That is a significant practical difference from a contract claim.
Where it appears. Employment offers withdrawn after resignation from prior work. Subcontractor bids relied on in a general contractor’s bid. Franchise and dealership discussions. Assurances of continued financing.
And where it fails. As a route around the statute of frauds it succeeds only in some jurisdictions and only in narrow circumstances. Treating it as a general cure for the absence of a signed writing is a mistake.