Question: My physician hired a physician assistant (PA) whom he is going to pay an hourly salary. How do I bill for the PA? Tennessee Subscriber Answer: How you bill for a PA's services depends on the individual payer's guidelines. For Medicare you-ll follow incident-to rules when appropriate, or you-ll bill under the PA's own national provider identifier (NPI) and you-ll receive 85 percent of the Medicare fee schedule when one of the following applies: - the doctor is not available for direct supervision - the patient is new - the patient is being seen for a new problem. Some other payers also use incident-to guidelines. Some, however, have there own regulations about if and how you can bill for PA services. Incident-to rules: PAs and other nonphysician practitioners (NPPs) can bill "incident-to" the physician -- that is, under the physician's NPI -- for their services. The physician has to see the patient for the first visit and establish a plan of care that the NPP will follow during other visits. After the initial visit, the physician does not need to be part of the patient encounter or be in the exam room. The physician must be on-site and immediately available to assist the PA, however. Alternative: Many payers allow you to bill under the PA's NPI, often for a reduced reimbursement amount. Still other payers don't allow you to bill under a PA's number at all. Check with the individual payer to see if you should bill incident-to or under the PA's number. Remember: Your PA needs to be credentialed with the payer before you can bill for any services he provides.