5 CFR §844.304

1. (a)An individual retiring under this part is not entitled to elect to receive an alternative form of annuity under 5 U.S.C. 8420a, even if the individual meets the requirements for retirement under another part and would be entitled to elect an alternative form of annuity in connection therewith.
2. (b)Notwithstanding any other provision of this part, an annuity payable under this part will be computed under 5 U.S.C. 8415 if it commences or is reinstated under § 844.405 (b) or (c) of this part on or after:
   1. (1)The annuitant has satisfied the age and service requirements for retirement under 5 U.S.C. 8412 (a) through (f); or
   2. (2)The annuitant has reached age 62.