Section 407.1 - Basis and scope(a)Statutory basis. The supplementary medical insurance (SMI) program is authorized by Part B of title XVIII of the Social Security Act.(1) Section 1831 of the Act establishes the program.(2) Sections 1836 and 1837 set forth the eligibility and enrollment requirements.(3) Section 1838 specifies the entitlement periods, which vary depending on the time and method of enrollment and on the basis for termination.(4) Section 1843 sets forth the requirements for State buy-in agreements under which States may enroll, and pay the SMI premiums for, eligible individuals who are also eligible for cash assistance or Medicaid.(5) Section 104(b) of the Social Security Amendments of 1965 (Pub. L. 89-87 ) specifies the limitations that apply to certain aliens and persons convicted of subversive activities.(6) Sections 1836(b) and 1837(n) of the Act provide for coverage of immunosuppressive drugs as described in section 1861(s)(2)(J) of the Act under Part B beginning on or after January 1, 2023, for eligible individuals whose benefits under Medicare Part A and eligibility to enroll in Part B on the basis of ESRD would otherwise end with the 36th month after the month in which the individual receives a kidney transplant by reason of section 226A(b)(2) of the Act.(b)Scope. This part sets forth the eligibility, enrollment, and entitlement requirements and procedures for the following:(1) Supplementary medical insurance. (The rules about premiums are in part 408 of this chapter.)(2) The immunosuppressive drug benefit provided for under sections 1836(b) and 1837(n) of the Act, hereinafter referred to as the Part B-Immunosuppressive Drug Benefit (Part B-ID).53 FR 47204, Nov. 22, 1988, as amended at 87 FR 66505 , Nov. 3, 2022