In our OB practice, we have a hospitalist that we bill deliveries for under our group tax ID. This doctor does on call deliveries and also any other services needed when our pateint's present at the hospital, instead of our office. What is the correct way to bill for these services to get reimbursement from payers that the group tax ID is contracted with, but the Dr.'s NPI is not? Is there a modifier that can be use to indicate a hositalist?