In accordance with established guidance applicable to the collection of data on waiting, which has been in place since 1989, patients are placed on deferred admission waiting lists where: there are personal, social or medical constraints at the time of deciding to admit which prevent them from accepting a normal hospital admission date if offered, for example because of their business or holiday commitments; or they do not attend for an arranged hospital admission date and give no advance warning; or hospital admission for treatment has been arranged for them, but they were sent home at the time of admission, or shortly afterwards, because they were assessed as being clinically unsuitable for treatment at that time, or their admission is being arranged, on a "one-off" basis, to give carers respite from their caring responsibilities.The all-Scotland deferred admission waiting list is routinely in excess of 20,000.