It depends on your insurance carrier. I would check with each of your provider service reps. For surgery with Medicare, we bill 82 AS, some of our other carriers, PA BCBS requires 80 AS, railroad medicare wants just an AS. As far as office visits, most of the commercial carriers want them billed under the doctor, with Medicare we bill under the Physician Assistant unless incident to rules apply which you may want to look up on Medicare's website. Basically if the physician has seen the patient first and established the plan of care than subsequent visits you can bill under the doctors name with the doctors NPI, as long as he is also in the office, (he does not have to see the patient but has to be available). However, this is a pretty simple explanation, incident to can be complicated so I would pull up the specific rules on Medicare's website.