Final answer:
An insurance plan's co-pay is a fixed fee paid at the time of service, whereas coinsurance is a percentage of the service cost paid by the policyholder after meeting the deductible.
Step-by-step explanation:
The difference between an insurance plan's co-pay and coinsurance primarily lies in their payment structure.
A co-pay is a predetermined flat fee that a policyholder pays at the time of service, such as $20 for an office visit or $250 for an emergency room visit.
In contrast, coinsurance refers to the percentage of the service cost that the patient is responsible for after their deductible has been met.
For instance, with a 20% coinsurance rate, the patient would be responsible for paying 20% of the total costs, while the insurance company would cover the remaining 80%.