A copayment is a fixed fee (for example, $15) that you pay for a covered health care service, usually at the time you receive the service. The amount can vary by the type of covered health care service.
Coinsurance is your share of the costs of a covered health care service, calculated as a percent (for example, 20%) of the allowed amount for the service. You pay coinsurance plus any annual deductibles you owe in the plan year. For example, if the health insurance plan’s allowed amount for an office visit is $100 and you’ve met your deductible, your coinsurance payment of 20% would be $20. The health insurance plan pays the rest of the allowed amount.