Which of the following best defines co-insurance?

Co-insurance refers to the percentage of the service cost that is shared between the patient and the insurance provider after the deductible has been met. This means that once a policyholder has paid their deductible, they are responsible for a specific percentage of the total cost for covered health care services, while the insurance company covers the remaining percentage. This arrangement helps to distribute costs between the insurer and the insured, making it an integral part of many health insurance plans.

The other options represent different insurance concepts that are not related to co-insurance. The fixed fee for healthcare visits refers to co-payments rather than co-insurance. An annual limit on out-of-pocket expenses pertains to maximum monetary thresholds for patient expenditures, which is a separate concept from co-insurance. Finally, comprehensive health coverage for low-income families describes a specific type of health plan and does not accurately reflect the definition or function of co-insurance. Thus, understanding that co-insurance is fundamentally about shared costs after meeting a deductible clarifies why the definition provided in this option is the most accurate.