Coding Cues: Avoiding "incident to" situations with ancillary personnel

I'm a PA, employed by a company owning multiple skilled nursing facilities in our city. I don't have provider numbers with various insurers, but I see patients with the oversight of an MD who's not always onsite. My services are being billed with the provider numbers of the "supervising" physician. I'm new to practice, so I'm not sure whether this is a problem? Is it?