When your doctor is asked to give medical information about you in the form of a report, letter or certificate, the request kick starts a series of processes.  This takes time and is not always straightforward or simple to complete. Some of the information is not available easily and will mean the doctor has to sort and select the right information for the request.  The doctor also must establish who is funding this work and if it is not part of their NHS work, agree a fee for this.