45.—(1) The leaver PIA index adjustment for an amount of accrued additional pension is calculated in accordance with paragraph (2).
(2) The leaver PIA index adjustment is the amount by which the annual rate of a pension of an amount equal to the amount of accrued additional pension would have been increased in the leaving year under PIA 1971 if—
(a)that pension were eligible to be so increased; and
(b)the beginning date for that pension were the day after the relevant last day.