Question: On a bilateral procedure, should we bill the procedure twice with one procedure appended with modifier -50 and the other one with no modifier? Kansas Subscriber Answer: The answer depends on the insurer. Medicare and some carriers insist on one line, such as: Many private payers prefer two lines, for example: For these payers, billing on two lines will cause the carriers to reject the second code as a duplication of services, and carriers will reimburse the first code only (that is, they will pay only for a unilateral procedure). You should check with your payer and get its guidelines in writing to avoid denials and to ethically maximize reimbursement. If you can't get the carrier's rules in writing, track how explanation of benefits comes in and how payers want the claims. Keep a grid of the codes with each carrier's coding preferences and any other payer-specific information, such as global surgical periods.