Contract and Commercial Law Review
Promissory estoppel is an important adjunct to contract law, allowing non-contractual promises to be legally binding under prescribed conditions. These conditions include reliance by the promisee, as the doctrine serves to protect reasonable reliance induced by certain types of promises. Typically, the conditions also include a requirement that it would be inequitable for the promisor to go back on the promise. This inequity requirement reflects the nature of promissory estoppel as a creature of the law of equity. Beyond this, however, considerable uncertainty surrounds the inequity element. For example, there are diverging views as to whether it embodies a distinct requirement, or whether it simply encapsulates the question that the doctrine’s other conditions together answer. If it does embody a distinct requirement, opinion further differs on whether its role is to inquire into specific considerations, or is to call for an overall (that is, subsuming the other conditions) assessment of the fairness of letting a promise be broken. And if it does mandate a specific enquiry, the set of factors it is meant to investigate, and how they are to be analysed, remains remarkably unknown. As Lord Justice Beatson, Lord Burrows and John Cartwright note, ‘there is little… guidance about’ what factors ‘will make it “not inequitable” for a person to go back on such a promise’.
Marcus Moore, "When Is It Fair to Break Promises? Illuminating Promissory Estoppel's Inequity Requirement" (2023) 1:3 Contract & Comm L Rev 161.