(5)(a)In a case referred to in clause (d) of sub-rule (1), the tax payable by the assessee on his total income of the previous year in which the payment in commutation of pension is received (such previous year being hereafter in this sub-rule referred to as the relevant previous year) shall be reduced by the amount, if any, by which the tax on the payment in commutation of pension included in the total income of the relevant previous year, calculated at the average rate of tax applicable to such total income, exceeds the tax on the amount of such payment, calculated at the rate of tax determined under clause (b).(b)The total income of the assessee in respect of each of the three previous years immediately preceding the relevant previous year shall be increased by an amount equal to one-third of the amount of payment in commutation of pension included in the total income of the relevant previous year, and the average rate of tax for each of the said three previous years shall be calculated as if the total income so increased were the total income of that previous year; and the average of the average rates of tax so calculated for the three previous years shall, for the purposes of clause (a), be the rate of tax determined under this clause.
