5 C.F.R. § 831.407

(a) At the time of retirement CSRS (or under FERS, if transferred from CSRS), a person may use the balance of a voluntary contribution account to purchase one of the following types of additional annuity:

(1) Annuity without survivor benefit; or

(2) Reduced annuity payable during the life of the employee or Member with one-half of the reduced annuity to be payable after his or her death to a person, named at time of retirement, during the life of the named person.

(b) Any natural person may be designated as survivor under paragraph (a)(2) of this section.

(c) If the applicant for retirement elects an annuity without survivor benefit, each $100 credited to his or her voluntary contribution account, including interest, purchases an additional annuity at the rate of $7 per year, plus 20 cents for each full year, if any, he or she is over age 55 at date of retirement.

(d) If the applicant for retirement elects an annuity with survivor benefit, each $100 credited to his or her voluntary contribution account, including interest, purchases an additional annuity at the rate of $7 per year, plus 20 cents for each full year, if any, he or she is over age 55 at date of retirement, multiplied by the following percentage:

(1) Ninety percent of such amount if the named person is the same age or older than the applicant for retirement, or is less than 5 years younger than the applicant for retirement;

(2) Eighty-five percent if the named person is 5 but less than 10 years younger;

(3) Eighty percent if the named person is 10 but less than 15 years younger;

(4) Seventy-five percent if the named person is 15 but less than 20 years younger;

(5) Seventy percent if the named person is 20 but less than 25 years younger;

(6) Sixty-five percent if the named person is 25 but less than 30 years younger; and

(7) Sixty percent if the named person is 30 or more years younger.