42 CFR §406.22

1. (a)Individual age 65 or over. For an individual who has attained age 65, before January 1, 2023, the following rules apply:
   1. (1)If the individual enrolls during the 3 months before the first month of eligibility, entitlement begins with the first month of eligibility.
   2. (2)If the individual enrolls in the first month of eligibility, entitlement begins with the following month.
   3. (3)If the individual enrolls during the month after the first month of eligibility, entitlement begins with the second month after the month of enrollment.
   4. (4)If the individual enrolls in either of the last 2 months of the enrollment period, entitlement begins with the third month after the month of enrollment.
2. (b)Individual age 65 or over. For an individual who has attained age 65 on or after January 1, 2023, the following rules apply:
   1. (1)If the individual enrolls during the first 3 months of their initial enrollment period, entitlement begins with the first month of eligibility.
   2. (2)If an individual enrolls during the last 4 months of their initial enrollment period, entitlement begins with the month following the month of enrollment.
3. (c)Individual under age 65. For an individual who has not attained age 65 and who satisfies the requirements of § 406.20(c) before January 1, 2023, the following rules apply:
   1. (1)If the individual enrolls before the month in which he or she meets the requirements of § 406.20(c), entitlement begins with the month in which the individual meets those requirements.
   2. (2)If the individual enrolls in the month in which he or she first meets the requirements of § 406.20(c), entitlement begins with the following month.
   3. (3)If the individual enrolls in the month following the month in which he or she meets the requirements of § 406.20(c), entitlement begins with the second month after the month of enrollment.
   4. (4)If the individual enrolls more than one month after the month in which he or she first meets the requirements of § 406.20(c), entitlement begins with the third month after the month of enrollment.
4. (d)Individual under age 65. For an individual who has not attained age 65 and who first satisfies the requirements of § 406.20(c) on or after January 1, 2023, the following rules apply:
   1. (1)For individuals who enroll during the first 3 months of their IEP, entitlement begins with the first month of eligibility.
   2. (2)If an individual enrolls during the month in which they first become eligible or any subsequent month of their IEP, entitlement begins with month following the month of enrollment.