## Facts

- The Carbolic Smoke Ball Company produced and sold a product claimed to prevent influenza and related ailments.
- The company advertised that £100 would be paid to any person who contracted influenza or a respiratory disease after using the smoke ball three times daily for two weeks as instructed.
- The advertisement specified a £1000 deposit with the Alliance Bank to show sincerity.
- Mrs. Carlill used the smoke ball as directed and subsequently contracted influenza.
- Mrs. Carlill claimed the £100 reward from the company, which was refused, resulting in legal proceedings.

## Issues

1. Whether the advertisement constituted a binding offer or was merely a sales puff or invitation to treat.
2. Whether an offer could be made to the world at large and be legally enforceable.
3. Whether Mrs. Carlill needed to communicate her acceptance, or if performance sufficed.
4. Whether sufficient consideration was provided by Mrs. Carlill for the company’s promise.

## Decision

- The Court of Appeal held that the advertisement was a binding offer for a unilateral contract, not a mere puff or invitation to treat.
- The court found that the £1000 deposit demonstrated clear intent to be legally bound.
- It was established that such an offer could be made to the public at large and was accepted by anyone who performed the specified conditions.
- Acceptance through performance, without explicit communication, was valid in unilateral contracts.
- Consideration was found both in the purchase of the smoke ball and in the inconvenience suffered by Mrs. Carlill in using it as directed.
- Judgment was entered in favor of Mrs. Carlill, entitling her to the £100 reward.

## Legal Principles

- An advertisement may constitute a valid unilateral offer if it demonstrates clear intention to be legally bound.
- In unilateral contracts, acceptance is made through complete performance of conditions, not necessarily by explicit communication.
- Consideration can include the inconvenience, effort, or detriment incurred by the performing party, not just direct benefit to the promisor.
- The distinction between an offer and an invitation to treat requires objective assessment of intent and clarity of terms.
- Offers made to the world at large may result in enforceable contracts with those who fulfill the specified terms.

## Conclusion

The decision in Carlill v Carbolic Smoke Ball Co [1893] 1 QB 256 established that clear, specific advertisements can be binding unilateral offers, accepted by performance and supported by consideration, thereby shaping the modern doctrine of contract formation and protection against deceptive advertising.