5 C.F.R. § 847.604 – Methodology for determining deficiency.

(a) When an event listed in the left column of the table in Appendix A to this subpart occurs, OPM will compute the deficiency, as follows:
1. (1) As of the date of computation under § 847.603, OPM will determine—
  1. (i) The present value of the annuity including credit for the NAFI service under § 847.605;
  2. (ii) The present value of the annuity without credit for the NAFI service under § 847.606 or § 847.607, as applicable; and
  3. (iii) The amount credited to the employee from a transfer to the Fund under subpart E of this part including earnings under § 847.507.
2. (2) OPM will add the amount determined under paragraphs (a)(1)(ii) and (iii) of this section and subtract that sum from the amount determined under paragraph (a)(1)(i) of this section.
(b) If the amount determined under paragraph (a)(2) of this section is greater than zero, the deficiency is equal to that amount.
(c) If no event listed in the left column of the table in Appendix A to this subpart occurs—that is, the additional service credit does not cause an increase in an employee annuity or a survivor annuity actually paid—or, if the amount determined under paragraph (a)(2) of this section is less than or equal to zero, the deficiency equals zero.