Initially there can be significant problems in identifying what an offer actually is. An offer must be distinguished from and invitation to treat which is generally just an indication that one party is trying to elicit offers from the other. Invitations to treat include newspapers advertisements (Partridge v Crittenden), goods in shop windows (Fished v Bell) and goods on shop shelves (Pharmaceutical society of GB v Boots). Even if a sign in a shop window declares “special offer” it is still not legally an offer.
All these distinctions are well established but there is some difficulty in separating an invitation to treat from a unilateral offer. Unilateral offers are ones made to the entire world which generally require some conduct to fulfil. In Carlill v Carbolic Smoke Ball the claimant tried to get compensation promised to customers who, responding to an advert, used a product and still contracted influenza (flu). It was held that the advert was so specific it was lifted above and invitation to treat, thus becoming an offer.The difficulty this poses for lawyers is where the distinction lies. How specific does and advertisement have to be in order to qualify as an offer? Not only do consumers suffer from this confusion but retailers too, perhaps finding themselves inadvertently making unilateral offers to which they will be bound –