Question: A patient's primary insurance had a $15 copay, which we collected from the patient at checkout. The primary insurance paid for the patient's office visit, and, since we already collected the copay, the claim is paid in full. If we had not collected the copay at the time of service, could we bill the secondary insurance for this amount? Should we have billed anything to the secondary insurance? South Dakota Subscriber Answer: Whether you can bill the secondary in-surance for a copay will depend on the specific coverage the secondary carrier offers. Billing can get very confusing when a patient has primary and secondary insurance. You should always abide by what the primary insurance dictates first. A secondary insurance is there to cover whatever the primary doesn't cover -- but this coverage may or may not include copays. Standard procedure would be to rollover the claim after the primary pays it and submit it to the secondary for the copayment, experts say. Then, once the secondary payer processes the claim, the account will either show a credit balance or no balance, depending on the coverage offered by the secondary insurance. You can then process a refund to the patient for whatever the credit balance is, up to the amount of the copayment. The answers to the Reader Questions and You Be the Billing Expert were reviewed by Barbara J. Cobuzzi, MBA, CPC-OTO, CPC-H, CPC-P, CPC-I, CHCC, president of CRN Healthcare Solutions in Tinton Falls, N.J. and senior coder and auditor for The Coding Network.