Roscorla v Thomas [1842] is the foundational authority for the principle that past consideration is no consideration, establishing that a promise made after a transaction is completed is generally unenforceable. The ruling reinforces that binding contracts require a contemporaneous exchange of sufficient consideration rather than a reliance on acts already performed.

Facts of the Case

A plaintiff purchased a horse from the defendant for £30. After the sale was concluded, the defendant gave an oral warranty asserting that the horse was “sound and free from vice”. This statement proved to be untrue, and the plaintiff subsequently sued the defendant for breach of contract based on the broken warranty.

Legal Issues

The central issue was whether the defendant’s subsequent warranty was a legally enforceable promise. The court had to determine if the original purchase price — an act already performed — could serve as valid consideration for a new promise made after the contract was already finalised.

Judgement

The court ruled in favour of the defendant, holding that the warranty was unenforceable for want of consideration. Lord Denman CJ reasoned that:

  • The only promise “coextensive” with the original consideration was the delivery of the horse upon request.
  • The precedent sale imposed no other duties or obligations on the seller.
  • Because the sale was finished before the warranty was provided, the consideration was “past and executed” and could not support the later express promise.

Authority and Significance

  • Past consideration rule: this case is the leading authority for the principle that consideration must be provided in return for the specific promise being enforced; acts performed prior to the promise do not count.
  • Coextensive promise: a promise must be coextensive with the consideration provided. A completed sale cannot support an additional subsequent warranty without new consideration.
  • Bargain theory: it underscores the distinction between an enforceable bargain and a subsequent gratuitous promise, which the law treats as a non-binding gift.
  • Contextual criticisms: modern commentators note that the outcome might be considered unsatisfactory if the court had instead viewed the sale and warranty as “one overall transaction” — a “benevolent approach” often taken in more contemporary commercial cases.