Breach of promise describes a failure to fulfil a legally enforceable promise, typically arising where a party does not perform obligations created by a contract, deed or clear undertaking relied on by another. In modern UK and Irish practice the concept is usually analysed through contract law (breach of contract) or, in some circumstances, estoppel or misrepresentation, rather than as a standalone cause of action.Historically, “breach of promise of marriage” was a recognised action, but this has been abolished in England and Wales and Northern Ireland, and is not generally available in Scotland or Ireland. Today, references to breach of promise in litigation, legal correspondence or advice usually concern:- a contractual promise (e.g. failure to pay, supply, complete a transaction or honour a settlement); or - a non‑contractual assurance giving rise to reliance-based remedies.Across England and Wales, Scotland, Northern Ireland and Ireland, key issues include: whether a legally binding promise exists, the scope of that promise, breach, causation, and the appropriate remedy (damages, specific performance, injunction or other relief). Usage is broadly consistent, but terminology in pleadings is normally “breach of contract” rather than “breach of promise”.