Medical billers process services provided to patients and submit claims to insurance companies. They follow up with the claim to ensure it is processed and paid in a timely manner. Any part of the services that are not covered by insurance is then billed to the patient. For certain medical procedures, medical billers also file insurance paperwork for pre-authorization to confirm insurance coverage for the procedure. Medical practices and healthcare facilities rely on medical billers to follow claims and reimbursements to bring in a steady stream of revenue.