If these are outside the consolidated billing requirements then it is the POS. When a patient is a registered patient in an inpatient setting such as a SNF and they are not discharged prior to having services at the ASC then you have use the SNF as the POS since that is where the patient is registered as a patient. This is covered in the Medicare manual under POS billing. If it is covered under consolidated billing then you do need to bill the ASC directly. from Medicare:
SNF Consolidated Billing
Overview on Skilled Nursing Facility (SNF) Consolidated Billing (CB):
In the Balanced Budget Act of 1997, Congress mandated that payment for the majority of services provided to beneficiaries in a Medicare covered SNF stay be included in a bundled prospective payment made through the Part A Medicare Administrative Contractor (MAC) to the SNF. These bundled services had to be billed by the SNF to the Part A MAC in a consolidated bill. No longer would entities that provided these services to beneficiaries in a SNF stay be able to bill separately for those services. Medicare beneficiaries can either be in a Part A covered SNF stay which includes medical services as well as room and board, or they can be in a Part B non-covered SNF stay in which the Part A benefits are exhausted, but certain medical services are still covered though room and board is not.
The consolidated billing requirement confers on the SNF the billing responsibility for the entire package of care that residents receive during a covered Part A SNF stay and physical, occupational, and speech therapy services received during a non-covered stay. Exception: There are a limited number of services specifically excluded from consolidated billing, and therefore, separately payable.
For Medicare beneficiaries in a covered Part A stay, these separately payable services include:
•physician's professional services;
•certain dialysis-related services, including covered ambulance transportation to obtain the dialysis services;
•certain ambulance services, including ambulance services that transport the beneficiary to the SNF initially, ambulance services that transport the beneficiary from the SNF at the end of the stay (other than in situations involving transfer to another SNF), and roundtrip ambulance services furnished during the stay that transport the beneficiary offsite temporarily in order to receive dialysis, or to receive certain types of intensive or emergency outpatient hospital services;
•erythropoietin for certain dialysis patients;
•certain chemotherapy drugs;
•certain chemotherapy administration services;
•radioisotope services; and
•customized prosthetic devices.
For Medicare beneficiaries in a non-covered stay, only therapy services are subject to consolidated billing. All other covered SNF services for these beneficiaries can be separately billed to and paid by the Medicare contractor.
Physicians, non-physician practitioners, and suppliers should contact their Part B MAC or Durable Medical Equipment (DME) MAC with questions about SNF consolidated billing. There is also additional information about SNF consolidated billing on the CMS Medicare Learning Network (MLN) Publications webpage.
Institutional providers should contact their Part A MAC with questions about SNF consolidated billing. There is also additional information about SNF consolidated billing on the CMS Medicare Learning Network (MLN) Publications webpage.
