20 C.F.R. § 416.2030
(a) Payment level. The level of State supplementary payments may vary for each category the State elects to include in its federally administered supplement. These categorical variations of payment levels must be specified in the agreement between the Commissioner and the State. If any State has in effect for July 1974 an agreement which provides for variations in addition to those specified in this section, the State may, at its option, continue such variations but only for periods ending before July 1, 1976.
(2) Living arrangements. In addition, a State may elect up to six variations in recognition of the different needs which result from various living arrangements. If a State elects six payment level variations based on differences in living arrangements, one of these six variations must apply only to individuals in Medicaid facilities, that is, facilities receiving title XIX payments with respect to such persons for the cost of their care (see § 416.211(b)(1)). In any event, States are limited to one payment level variation for residents of Medicaid facilities. Types of other living arrangements for which payment variations may be allowed include arrangements such as:
[40 FR 7640, Feb. 21, 1975, as amended at 50 FR 48579, Nov. 26, 1985; 56 FR 41455, Aug. 21, 1991; 62 FR 38455, July 18, 1997]