42 CFR §430.16

1. (a)Timing.
   1. (1)A State plan or plan amendment will be considered approved unless CMS, within 90 days after receipt of the plan or plan amendment in the regional office, sends the State—
      1. (i)Written notice of disapproval; or
      2. (ii)Written notice of any additional information it needs in order to make a final determination.
   2. (2)If CMS requests additional information, the 90-day period for CMS action on the plan or plan amendment begins on the day it receives that information.
2. (b)Notice of final determination.
   1. (1)The Regional Administrator or the Administrator notifies the Medicaid agency of the approval of a State plan or plan amendment.
   2. (2)Only the Administrator gives notice of disapproval of a State plan or plan amendment.