45 CFR § 205.5 - Plan amendments.
(a) State plan requirements. A State plan under title I, IV-A, X, XIV, or XVI (AABD) of the Social Security Act must provide that the plan will be amended whenever necessary to reflect new or revised Federal statutes or regulations, or material change in any phase of State law, organization, policy or State agency operation.
(b) Federal financial participation. Except where otherwise provided, Federal financial participation is available in the additional expenditures resulting from an amended provision of the State plan as of the first day of the calendar quarter in which an approvable amendment is submitted or the date on which the amended provision becomes effective in the State, whichever is later.