42 CFR §417.580

1. (a)Basis. This subpart implements those portions of section 1876 (a), (e), and (g) of the Act that pertain to the amount CMS pays an organization for its Medicare enrollees who are enrolled on a risk basis.
2. (b)Scope. This subpart sets forth—
   1. (1)Method of payment;
   2. (2)Procedures for determining the HMO's or CMP's payment rate; and
   3. (3)Procedures for determining the additional benefits (and their value) the HMO or CMP must provide to its Medicare enrollees.