In our clinic, there is no penalty to patients who do not show up for their appointments, and this costs our clinic in wasted clinician and staff time and energy.  Instituting a 24 hour cancellation policy with patients being responsible for a small sum of money in the event that they do not show up or cancel without adequate notice would encourage them to be responsible in communicating in advance when they will be unable to make a scheduled appointment.  Most private clinics keep a credit card on file for each patient just for this kind of situation.