What is IOP Billing and How Does It Work? IOP (Intensive Outpatient Program) billing involves using HCPCS codes like H0015 (substance use IOP) and S9480 (mental health IOP) to submit claims for bundled daily services. Most insurers require pre-authorization, condition code 92 (for Medicare), and a minimum of 9 hours of weekly treatment to qualify for reimbursement. Proper coding, medical necessity documentation, and adherence to payer guidelines help ensure claim approval and avoid denials.