Invitations to treat are not offers (see: Invitation to treat). For example, putting an item on display in a shop window with a price label is not an offer, it is merely an invitation to treat.
Pre-contractual negotiations, particularly in Conveyancing, may have the appearance of offers, but it will be necessary to satisfy the courts that a real offer has been made.
Tenders (see: Tender) are not offers unless they are construed as a Unilateral contract.
An offer can be withdrawn (revoked) at any time up to acceptance, provided it is communicated appropriately to the offeree. There are a few of complications with this.
Placing a notice of the withdrawal in the post does not constitute the withdrawal; it has to be received and understood by the offeree (see: Byrne vvan tienhov en (1880)).
If the offer forms the basis for a unilateral contract, it can be difficult to revoke. Typically the offerer must take reasonable steps to revoke the offer in the same form as it was originally made. For example, if the offer was made in a newspaper, then it should probably be revoked the same way. Moreover, it is particularly problematic if a unilateral offer is revoked before full completion of the act that constitutes the acceptance. In Carlill v Carbolic, for example (see: Carlill v carbolic smoke ball co (1893)), Mrs Carlill was able to demonstrate that she had completed the acceptance, so Carbolic could not have