Promissory estoppel is a rule in common law, it mainly expresses the idea that one party cannot change or act against his/her promise. The definition of promissory estoppel is that: Promissory estoppel is the doctrine which prevents a party from breaking a promise that was not supported by consideration if: This conduct is unconscionable; The other party believed the promise and will suffer a significant loss(Meagher Lehane Gummow 2002 ). Certain elements must be established to invoke promissory estoppel. A promisor—one who makes a promise—makes a gratuitous promise that he should reasonably have expected to ...