42 C.F.R. § 411.102 : Public Health — CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES — MEDICARE PROGRAM — EXCLUSIONS FROM MEDICARE AND LIMITATIONS ON MEDICARE PAYMENT — LIMITATIONS ON PAYMENT FOR SERVICES COVERED UNDER GROUP HEALTH PLANS: GENERAL PROVISIONS — Basic prohibitions and requirements

(a) ESRD.
(1) A group health plan of any size-
(i) May not take into account the ESRD-based Medicare eligibility or entitlement of any individual who is covered or seeks to be covered under the plan; and
(ii) May not differentiate in the benefits it provides between individuals with ESRD and other individuals covered under the plan, on the basis of the existence of ESRD, or the need for dialysis, or in any other manner.
(2) The prohibitions of paragraph (a) of this section do not prohibit a plan from paying benefits secondary to Medicare after the first 18 months of ESRD-based eligibility or entitlement.
(b) Age. A GHP of an employer or employee organization of at least 20 employees-
(1) May not take into account the age-based Medicare entitlement of an individual or spouse age 65 or older who is covered (or seeks to be covered) under the plan by virtue of current employment status; and
(2) Must provide, to employees age 65 or older and to spouses age 65 or older of employees of any age, the same benefits under the same conditions as it provides to employees and spouses under age 65.
(c) Disability. A GHP of an employer or employee organization of at least 100 employees may not take into account the disability-based Medicare entitlement of any individual who is covered (or seeks to be covered) under the plan by virtue of current employment status.

42 C.F.R. §411.102