.Physician owned hospitals, who are allowed to turn away patients based on need. They don't have to take assignment.
I should have been more explicit when I tagged hospitals that do not accept federal funds as being exempt from Medicare assignment. Yes, privately owned hospitals that do not receive any federal monies, including from Medicaid patients, are not required to accept assignment.
Hospital inpatient charges do not fall under excess charges but their outpatient services, such as ER could bill for excesses subject to the cap.
Aren't "physician's services" billed to Part B, even as an inpatient?
Yes, but that has nothing to do with hospitals that do or do not take assignment.