Co-Insurance

What Does Co-Insurance Mean?
A co-sharing agreement between the insured and the insurer under a health insurance policy which provides that the insured will cover a set percentage of the covered costs after the deductible has been paid. Similar to co-pay insurance plans except co-pays require the insured to pay a set dollar amount at the time the service is rendered.

Investopedia explains Co-Insurance
For example, an 80/20 coinsurance plan with a $300 deductible requires the insured to pay 20% of the covered costs after the deductible as been paid, while the insurance company will be liable for the remaining 80%. Today, with the growing cost of prescription drugs and medical expenses, more and more employers have switched from co-pay plans to coinsurance plans to reduce employee-benefit costs.