A copayment or “copay” as it is sometimes called, is a flat fee that the patient pays at the time of service. After the patient pays the fee, the plan usually pays 100 percent of the balance on eligible services. Eligible services are those services that the plan includes in its coverage. The fee usually ranges between $10 and $40. Copayments are common in HMO products and are often characteristic of PPO plans as well.