Set your own appointment cancellation reasons so that you can report on them using the Appointments Report.
Go to Settings > Diary > Appointment Cancellation Reasons. You need to have Level 4 (Administrator) permissions.
New Cancellation Reason
Select New Cancellation Reason
Type in your cancellation reason
Edit Cancellation Reason
If you wish to edit a cancellation reason, click on the edit icon to the right of the reason.
Make any edits you wish to make and select Save
If you no longer wish to use the cancellation reason, mark it as Hidden and Save.