A patient can make many appointments with one or more doctors in the clinic, and a doctor can accept appointments with many patients. However, each appointment is made with only one doctor and one patient. Emergency cases do not require an appointment. However, for appointment management purposes, an emergency is entered in the appointment book as “unscheduled.” If kept, an appointment yields a visit with the doctor specified in the appointment. The visit yields a diagnosis and, when appropriate, treatment. With each visit, the patient’s records are updated to provide a medical history Each patient visit creates a bill. Each patient visit is billed by one doctor, and each doctor can bill many patients. Each bill must be paid. However, a bill may be paid in many installments, and a payment may cover more than one bill. A patient may pay the bill directly, or the bill may be the basis for a claim submitted to an insurance company. If the bill is paid by an insurance company, the deductible is submitted to the patient for payment.