We have been billing for our ASC since January. We use a CMS 1500 since they do not accept UB04 for part B. We have been putting the Dr. as Rendering provider and putting Dr's NPI in 24J and then listing the Facility as the Billing provider with the facility NPI. These claims are now denying stating the Dr. is not affiliated with the group...however this isn't a group and I was told by our credentialing dept that Dr's don't need to be linked to a facility to bill. Should facility NPI go in 24J and Dr's NPI go in 33?