5 CFR § 831.702 - Adjustment of annuities.
(a)
(1) An annuity which includes creditable National Guard technician service performed prior to January 1, 1969, shall be reduced by the portion of any benefits under any State retirement system to which an annuitant is entitled (or on proper application would be entitled) for any month in which the annuitant is eligible for State benefits based on the same pre-1969, service.
(2) Any cost-of-living increases in the State benefit shall require a corresponding deduction in the civil service annuity.
(3) Any cost-of-living increase to a civil service annuity shall apply to the gross annuity before deduction for benefits under any State retirement system.
(b) In the adjudication of claims arising under subchapter III of chapter 83 of title 5, United States Code, OPM shall take appropriate action to obtain the data that it considers necessary to assure the proper annuity deduction. Upon request by OPM, an annuitant shall promptly submit this data.