When can an offer to form a unilateral contract be revoked?

Answer 1

If you have a unilateral contract, then you have the right to revoke it. This is fairly basic contract law. For a contract to be binding and irrevocable both parties must understand and sign the contract.

Answer 2

If work has already started there is no offer that can be formed for a unilateral contract to be revoked. If no work has started both parties must agree to the revocation of the contract to avoid breech of contract.

Answer 3

In some situations, an offer can be revoked any time after it is made, up until when it is deemed lawfully accepted. The concept of revocation is sometimes attempted to be used to advocate against the necessity for the recognition of the formation of a contract, thus negating the possibility of liability for performance of a contract that does not exist (but consider implied-in-fact contracts). A revoked offer can no longer be lawfully accepted, and thus a contract based on it cannot be formed.

Revocation can be deemed to not be a lawful option for a contract party where detrimental reliance has already been made by the other party on the offer at the time the party wishes to revoke, in which case the contract is deemed formed, as long as there is sufficient consideration or a substitute therefor.