20 CFR §225.55

1. (a)Description—(1) New computation formula. If a new formula for computing or recomputing PIA's is enacted into law and the annuitant is eligible for the recomputation, the Board will recompute the PIA under the new formula.
   1. (2)Recomputation under different formula. In some cases, a PIA may be recomputed under a computation formula different from the formula used in the computation (or earlier recomputation) of the PIA. The annuitant must be eligible for a computation or recomputation under the different formula.
2. (b)Effective date of recomputation—(1) New computation formula. A PIA recomputed under a newly enacted formula is effective with the month as directed in the legislation that establishes the new formula. The new PIA formula applies when it produces a PIA that is higher than the amount on which the existing annuity is based.
   1. (2)Different computation formula. A PIA recomputed under a different formula is effective with the first month that the different formula produces a PIA that is higher than the PIA on which the existing annuity is based.