Which A/B MAC (A) or (B) to Bill for Laboratory Services Furnished to a

40.4.1 - Which A/B MAC (A) or (B) to Bill for Laboratory Services Furnished to a Medicare Beneficiary in a Skilled Nursing Facility (SNF) (Rev. 1, 10-01-03) Inpatient Part A beneficiary - SNF bills the A/B MAC (A) under Part A. The service is included in SNF PPS payment. Inpatient Part B beneficiary (benefits exhausted or no Part A entitlement) - SNFs may provide the service and bill the A/B MAC (A), may obtain the service under arrangement and bill the A/B MAC (A) under Part B, or may have agreement with a reference laboratory for the reference laboratory to provide the service and have the reference laboratory bill the A/B MAC (B) under Part B. Regardless of who bills, CMS policy requires that the service be paid under the fee schedule, whether or not the beneficiary is in a Medicare certified bed. Outpatient Part B - See inpatient Part B beneficiary (benefits exhausted or no Part A entitlement), immediately above.