jesus wept, you have come to the wrong place. disregard almost everything above. going to a close is not legally required but is general practice, you can assume there are other notes of interest in and the seller wants to wait and give all interested parties notice enough to submit an offer if that is their intent. An offer regardless of any conditions on either part is not legally binding until the missives are sent. if you want to upset a seller by all means put a deadline for acceptance on it, most sellers will see through this bravado and think you are an amateur, or plain cheeky unless it is an incredible offer or a house they think won't sell. can you imagine negotiating verbally and agreeing without formal offers, you can't sell a plant pot in shetland without an ordeal never mind a house.