(as defined in Section 2(a) of the Contracts Act 1950) when one person signifies to another his willingness to do or to abstain from doing anything, with a view to obtaining the assent of that other to the act or abstinence
Carbolic Smoke Ball Co. Ltd. advertised that they would pay a sum of 1,000 pounds to anyone who took their product for a certain duration and succumbed to influenza
Partridge v Crittenden: The defendant's advertisement for 'Quality Bramblefinch cocks, Bramblefinch hens, 25s each' was held to be an invitation to treat, not an offer
Coelho v The Public Services Commission: The advertisement for the post of Assistant Passport Officer was an invitation to qualified persons to apply, the applications were offers
Carlill v Carbolic Smoke Ball Co: The advertisement offering £100 to anyone who still caught influenza after using the smoke ball was held to be an offer
Harvey v Facey: Facey's telegram stating the lowest price for Bumper Hall Pen was held to be a mere response to a request for information, not an offer
Where an auctioneer invites bids, it is an invitation to treat. When a bidder makes a bid, it is an offer. The sale is complete when the auctioneer announces it by the fall of the hammer.
Payne v Cave: The defendant withdrew his bid before the fall of the auctioneer's hammer, which was held to be valid as every bidding is an offer that is not binding until assented to