Subject to paragraph (b) of this section, an annuity supplement is an amount equal to the old-age insurance benefit payable under title II of the Social Security Act, multiplied by a fraction—

The numerator of which is the annuitant's total service creditable under FERS, excluding military service not performed during an absence of leave without pay from civilian service, rounded to the nearest whole number of years not exceeding 40 years; and

The denominator of which is 40.

The benefit referred to in paragraph (a) of this section is computed—

As if the annuitant were age 62 and fully insured on January 1 of the year the annuity supplement commences;

Without regard to the Social Security earnings test (section 203 of the Social Security Act);

Without regard to the Social Security windfall elimination provisions (sections 215(a)(7) and 215(d)(5) of the Social Security Act); and

Using the actuarial reduction (section 202(q) of the Social Security Act) prescribed in the following table:

In computing the primary insurance amount—

The number of elapsed years used to compute the number of benefit computation years does not include the years beginning with the year in which the annuity supplement commences;

For an employee or Member who retires under §§ 842.205, 842.206, 842.209, or 842.211 before reaching the minimum retirement age, wages in calendar years beginning after the date of separation on which the retirement is based, are deemed to be zero.

Only basic pay for full calendar years of service creditable under FERS is taken into account in computing the retiree's wages for a benefit computation year;

For a benefit computation year after age 21 during which the retiree did not perform a full calendar year of service creditable under FERS the retiree's wages are deemed to equal the product of—

The National Average Wage Index (as determined by the Commissioner of the Social Security Administration) corresponding to that year, multiplied by

A fraction—

The numerator of which is the retiree's basic pay for his or her first full year of service creditable under FERS; and

The denominator of which is the National Average Wage Index (as determined by the Commissioner of the Social Security Administration) corresponding to the retiree's first full year of service creditable under FERS.