42 C.F.R. § 411.12
(a) Basic rule. Medicare does not pay for services usually covered under Medicare if the charges for those services are imposed by—
(b) Definitions. As used in this section—
Immediate relative means any of the following:
Member of the household means any person sharing a common abode as part of a single family unit, including domestic employees and others who live together as part of a family unit, but not including a mere roomer or boarder.
Professional corporation means a corporation that is completely owned by one or more physicians and is operated for the purpose of conducting the practice of medicine, osteopathy dentistry, podiatry, optometry, or chiropractic, or is owned by other health care professionals as authorized by State law.
(c) Applicability of the exclusion. The exclusion applies to the following charges in the specified circumstances:
(1) Physicians' services.
(2) Services other than physicians' services.