What does a 28 day exchange deadline mean?

The developer requires a fixed period ( usually 21 or 28 days) between reservation and exchange of contracts. It is up to the developer whether to strictly adhere to this deadline or whether to extend by say a week which may depend on your situation e.g. if your conveyancer is waiting for your mortgage instructions, the Local Search result has not been received or enquiries not yet satisfactorily replied to. If your reservation is cancelled because of failure to meet the deadline then you will either lose all your reservation fee or there may be deduction of administration costs set out in the reservation document and the balance returned to you.