Carlill v. Carbolic Smoke Ball Co. (1893)

IRAC Summary

Issue: Whether there was a binding contract between Mrs. Carlill and the Carbolic Smoke Ball Company through the advertisement of a reward for any person who used their product, the smoke ball, and contracted influenza.

Rule: A contract requires an offer that is clear, unequivocal, and communicated to the offeree, an acceptance of that offer, and consideration to show that the parties intend to be bound by the terms. Unilateral contracts are formed when a party promises something in exchange for the performance of an act by the other party. Acceptance occurs upon performance of the conditions stated in the offer.

Application: The company advertised that it would pay £100 to anyone who contracted influenza after using their smoke ball according to the instructions provided. Carlill used the product as directed and subsequently contracted influenza. The company argued that there was no contract as the advertisement was not an offer but a sales puff and there was no acceptance. However, since the advertisement contained a clear promise for payment in exchange for a specific act, it constituted an offer for a unilateral contract. Carlill’s use of the smoke ball as stipulated was the acceptance of the offer through performance, and her reliance on the promise was the consideration.

Conclusion: The court concluded that there was a legally binding unilateral contract between Carlill and the Carbolic Smoke Ball Company, and as such, the company was required to pay the £100 to Mrs. Carlill.

Detailed IRAC Outline


The primary issue is whether the advertisement by the Carbolic Smoke Ball Company constituted an offer to enter into a unilateral contract that could be accepted by anyone who performed the conditions stated in the advertisement, and whether Mrs. Carlill successfully accepted this offer, entitling her to the reward after contracting influenza despite using the product.


  1. Offer: An offer must be clear, unambiguous, and communicated to the offeree. It must indicate an intention to be bound upon acceptance.

  2. Unilateral Contracts: A unilateral contract involves a promise in exchange for an act. Acceptance is typically through full performance of the act.

  3. Acceptance: In unilateral contracts, acceptance is typically the performance of the condition of the offer.

  4. Consideration: Consideration is some value given by both parties to a contract that induces them to enter into an agreement to exchange mutual performances.


– The advertisement promised to pay £100 to any person who used the smoke ball and then contracted influenza, which is a clear representation of an offer to the public.

Unilateral Contracts:
– The advertisement can be interpreted as an offer for a unilateral contract where the Carbolic Smoke Ball Company promised to pay upon the occurrence of a specified act (using the smoke ball and contracting influenza despite this).

– Mrs. Carlill accepted the offer by performing the act required (using the smoke ball as directed) which constitutes acceptance in a unilateral contract.

– Mrs. Carlill’s action of using the smoke ball as per the instructions provided consideration in the form of reliance on the promise made in the advertisement, which required her to undertake certain actions and possibly forgo other treatments.


The court held that the Carbolic Smoke Ball Company’s advertisement constituted a legitimate offer for a unilateral contract, which Mrs. Carlill accepted through her performance of the act as specified in the advertisement. She provided consideration by altering her conduct in reliance on the promise. Therefore, a binding contract existed, and the company was obligated to pay Mrs. Carlill the £100 promised in the advertisement.

Discussion of the Case

Validity of the Advertisement as an Offer:
– The court rejected the argument that the advertisement was a sales puff or too vague to constitute an offer. Instead, it saw the promise as definite and the deposit of £1000 in the bank as evidence of the company’s intention to be bound.

Nature of Contractual Acceptance in Unilateral Contracts:
– The acceptance of an offer in a unilateral contract is not through communication of acceptance but rather through the performance of the condition.

Consideration and General Offers to the Public:
– The consideration was not solely the use of the smoke ball but also the potential detriment to Mrs. Carlill, who acted based on the company’s promise, altering her behavior and assuming the risk of the product’s failure.

Intent to Create Legal Relations:
– The company’s actions and the specificity of the offer indicated an intention to be legally bound, rather than making a mere declaration of intent or wish.

Implications of the Decision:
– The case established important precedents for contract law, particularly in relation to unilateral contracts, advertisements as offers, and the sufficiency of consideration through performance and reliance.

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