20 CFR 404.243 - Computation where you are eligible for a pension based on noncovered employment.
The provisions of § 404.213 are applicable to computations under the old-start method, except for paragraphs (c) (1) and (2) and (d) of that section. Your primary insurance amount will be whichever of the following two amounts is larger:
(a) One-half the primary insurance amount computed according to § 404.241 (before application of the cost of living amount); or
(b) The primary insurance amount computed according to § 404.241 (before application of the cost of living amount), minus one-half the portion of your monthly pension which is due to noncovered work after 1956 and for which you were eligible in the first month you became eligible for Social Security benefits. If the result is not a multiple of $0.10, we will round to the next lower multiple of $0.10. (See § 404.213 (b)(3) if you are not eligible for a monthly pension in the first month you are entitled to Social Security benefits.) To determine the portion of your pension which is due to noncovered work after 1956, we consider the total number of years of work used to compute your pension and the percentage of those years which are after 1956 and in which your employment was not covered. We take that percentage of your total pension as the amount which is due to your noncovered work after 1956.