(a) For the purposes of this subpart, the “adjusted social security disability benefit” is the benefit to which an annuitant is entitled under section 223 of the Social Security Act:

(1) For the month in which the annuity under this part commences, or is reinstated under § 844.405, or, if later, the first month for which the annuitant is entitled to both an annuity under this part and a social security disability benefit;

(2) Including, where appropriate, a reduction under section 224 of the Social Security Act, based on the amount of the disability annuity under this subpart without regard to paragraphs (b)(2) and (c)(2) of this section; and

(3) Adjusted by each cost-of-living increase effective under 5 U.S.C. 8462(b) beginning with the later of the month after the 12-month period referred to in paragraph (b)(1) of this section, or the first month for which the annuitant is entitled to both an annuity under this part and a social security disability benefit.

(b)(1) Except as otherwise provided in this part, the annuity payable under this subpart until the end of the 12th month beginning after the annuity commences (or is reinstated under § 844.405) is equal to 60 percent of the annuitant's average pay.

(2) For months for which the annuitant is also entitled to a social security disability benefit, the amount computed under paragraph (b)(1) of this section is reduced by 100 percent of the annuitant's adjusted social security disability benefit.

(c)(1) Except as otherwise provided in this part, the annuity under this subpart after the period described in paragraph (b)(1) of this section is equal to 40 percent of the annuitant's average pay.

(2) For months after the period described in paragraph (b)(1) of this section for which the annuitant is also entitled to a social security disability benefit, the amount computed under paragraph (c)(1) of this section is reduced by 60 percent of the annuitant's adjusted social security disability benefit.

(d) For months in which an annuity is reduced under paragraph (b) or (c) of this section, any reduction for survivor benefits is made after the reduction for social security benefits.