Seconding Sharon. The guidelines/references are likely in your provider contracts with each payor. I don't think I've ever seen a contract that would permit billing under a different physician.
In our practice, we have a 1 year training program (not an official fellowship) for fully certified ob/gyns to gain experience in complex pelvic surgery. It's a new clinician every year. I start the credentialing process 90 days before they first step foot in the door. Even 90 days is not enough for some carriers.
My opinion when hiring a new physician:
1) Start credentialing as early as possible.
2) Once they start, keep a chart of which carriers they are credentialed with. Update it regularly and keep your scheduling staff informed.
3) Only schedule patients for the new provider with fully credentialed carriers (or self pay).
4) To keep the new provider's schedule fuller, have your front desk funnel the credentialed payors to the new physician as much as possible.
Other options include having the new clinician provide global surgical care (postop, suture removal, etc.) In our practice, during the week we round on inpatients in the morning and afternoon. The new clinician could do one of those roundings, and the bill can be submitted under the participating clinician who also saw the patient the same day.
5) There may be instances where (for patient care reasons), you must schedule a patient with non-credentialed insurance. Inform the patient (in writing is a good idea) the new physician may not currently be participating, and they may be billed for out of network deductible/co-insurance, etc.
