Co-Insurance (also known as co-payment)

Co-insurance is the percentage of an approved claim that your insurer does not reimburse, so you must pay that share yourself. It is based on a percentage of the bill rather than a fixed dollar amount. This is different from a co-pay, which is a fixed amount paid for each bill.

If your hospital bill is $100 and your co-insurance is 20%, you pay $20 and the insurer pays the rest. It changes with the size of the bill.