The legal principle established in Carlill v Carbolic Smoke Ball Co is the concept of a unilateral contract, where an offer can be accepted by performing a specific act, rather than through a promise. This case is a landmark in contract law, illustrating that advertisements can constitute a binding offer if they demonstrate an intention to create legal obligations.
Unilateral contract:
The court recognised that the advertisement by Carbolic Smoke Ball Co was a unilateral offer to the world, which could be accepted by anyone who performed the conditions stated in the advertisement, namely using the smoke ball as directed and still contracting influenza (McGinnis, 1988; Jackson, 2018).
Intention to create legal relations:
The case highlighted the importance of intention to create legal obligations in contract formation. The court found that the company’s deposit of £1000 in a bank demonstrated a serious intention to be legally bound by the offer, countering the argument that the advertisement was mere puffery (McGinnis, 1988; Philip, 2008).
Acceptance by conduct:
The court ruled that acceptance of the offer did not require communication of acceptance to the offeror. Instead, performing the conditions of the offer (using the smoke ball and contracting influenza) constituted acceptance (McGinnis, 1988; Jackson, 2018).
In conclusion, Carlill v Carbolic Smoke Ball Co established the enforceability of unilateral contracts and clarified that advertisements can be considered offers if they show an intention to create legal obligations. This case remains a foundational precedent in contract law, illustrating how offers can be accepted through conduct and the significance of intention in forming binding agreements.
Click here to read a case summary of Carlill v. Carbolic Smoke Ball Company.
References
- McGinnis, J., 1988. Carlill v. Carbolic Smoke Ball Company: influenza, quackery, and the unilateral contract.. Canadian bulletin of medical history = Bulletin canadien d’histoire de la medecine, 5 2, pp. 121-41. https://doi.org/10.3138/CBMH.5.2.121
- Jackson, N., 2018. Carlill v Carbolic Smoke Ball Co [1893] 1 QB 256. Essential Cases: Contract Law 3e. https://doi.org/10.1093/he/9780191866135.003.0004
- Philip, M., 2008. Problem of Intention. Social Science Research Network. https://doi.org/10.2139/SSRN.1162013
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National Case Law Archive, 'What legal principle was established in Carlill v Carbolic Smoke Ball?' (LawCases.net, August 2025) <https://www.lawcases.net/analysis/what-legal-principle-was-established-in-carlill-v-carbolic-smoke-ball/> accessed 8 November 2025
