8. Mistake

Abstract

Course-focused and comprehensive, Poole’s Textbook on Contract Law provides an accessible overview of the key areas on the law curriculum. This chapter focuses on the legal treatment of ‘mistake’. It considers mistakes that prevent agreement (mutual or cross-purposes mistakes and unilateral mistake as to terms, particularly identity mistakes). It also examines the remedy of rectification when the contract does not accurately reflect what the parties agreed. It also considers the defence of non est factum. It then considers mistakes that are presumed to nullify consent if both parties entered into the contract under the same fundamental mistake. The doctrine of common mistake in English law is designed to protect the interests of third parties and to ensure certainty in transactions. A fundamental common mistake arises in cases where there is true impossibility or failure of consideration; the contract is automatically void and any money or property involved has to be returned. Distinctions can arise depending upon whether the impossibility is initial (common mistake) or subsequent (frustration doctrine). Categories of common mistake at common law include mistake as to subject matter (res extincta) and mistake as to ownership (res sua). A mistake as to quality will rarely be sufficiently fundamental to render the contract void. This chapter also discusses Lord Denning’s attempts to introduce an equitable jurisdiction to set aside on terms in cases of mistakes as to quality. These were rejected in Great Peace Shipping Ltd v Tsavliris (International) Ltd meaning that there is no remedial flexibility in such instances.