Doctors can charge for missed appointments. The American Medical Association states that such charges are allowable if a patient did not cancel 24 hours in advance and is aware that the doctor may impose such a charge.
No-show fees are typical in medicine because when a patient fails to appear for an appointment, the doctor's office loses revenue. The charges make up for some of that missed revenue and serve as an incentive for patients to stick to their schedules or to give notice if they cannot attend appointments. In addition, a patient can reschedule his appointment with the office staff when he gives proper notice ahead of time.