42 C.F.R. § 421.401 – Definitions.

For purposes of this subpart—

Appropriate MAC means a MAC that has a contract under section 1874A of the Act to perform a particular Medicare administrative function in relation to:

(1) A particular individual entitled to benefits under Part A or enrolled under Part B, or both;
(2) A specific provider of services or supplier; or
(3) A class of providers of services or suppliers.
Medicare Administrative Contractor (MAC) means an agency, organization, or other person with a contract under section 1874A of the Act.