Chwee Kin Keong v Digilandmall.com Pte Ltd

Chwee Kin Keong v Digilandmall.com Pte Ltd [2005] 1 SLR(R) 502 is a leading Court of Appeal decision on unilateral mistake in contract law, arising from an online pricing error. The Court clarified when equity will relieve a party from a contract where the other party knew or ought to have known of the mistake, applying the test of actual or constructive knowledge to the offeree's conscience.

An online retailer mistakenly listed commercial laser printers at approximately SGD 66 each instead of the correct price of several thousand dollars. Multiple purchasers placed orders for these printers in quick succession during the early morning hours, aware that the price was anomalously low. The retailer refused to honour the contracts and sought to set them aside on grounds of unilateral mistake.

Whether contracts formed through an online pricing error may be set aside in equity on the ground of unilateral mistake where the purchasers knew or ought to have known of the mistake.

The Court of Appeal held that equity would grant relief for unilateral mistake where the non-mistaken party had actual or constructive knowledge of the mistake at the time of contract formation. On the facts, the purchasers either knew or ought to have known that the price was erroneous, and it would be unconscionable to hold the retailer to the contracts. The contracts were set aside.

A contract may be set aside in equity for unilateral mistake of fact if: (1) one party was mistaken as to a fundamental term; (2) the non-mistaken party had actual knowledge of the mistake or the mistake was so obvious that the non-mistaken party should have known of it (constructive knowledge); and (3) it would be unconscionable in all the circumstances to hold the mistaken party to the contract.

The Court adopted a test rooted in the conscience of the non-mistaken party: relief is available where that party knew or ought to have known of the mistake, making enforcement unconscionable. The Court rejected a narrower test requiring actual knowledge only, holding that constructive knowledge suffices if the error is obvious to a reasonable person in the position of the offeree. On the evidence, the extremely low price, the time of transactions, and the speed and volume of orders indicated that purchasers either knew or should have known the price was a mistake.

The Court made observations on the application of common law and equitable principles to electronic commerce, noting that traditional doctrines apply but must be adapted to the speed and automated nature of online transactions.

This case is the foundational Singapore authority on unilateral mistake in contract formation and is essential teaching material on the limits of offer-and-acceptance doctrine, equitable intervention, and e-commerce contracting. It clarifies that both actual and constructive knowledge of a mistake can ground relief, emphasizing the role of conscience and unconscionability in equity.

Chwee Kin Keong v Digilandmall.com Pte Ltd [2005] 1 SLR(R) 502 (CA)