filing month
(3) Determination of adjusted seasonal installment (A) In general In the case of any required installment, the amount of the adjusted seasonal installment is the excess (if any) of— (i) 100 percent of the amount determined under subparagraph (C), over (ii) the aggregate amount of all prior required installments for the taxable year. (B) Limitation on application of paragraph This paragraph shall apply only if the base period percentage for any 6 consecutive months of the taxable year equals or exceeds 70 percent. (C) Determination of amount The amount determined under this subparagraph for any installment shall be determined in the following manner— (i) take the taxable income for all months during the taxable year preceding the filing month, (ii) divide such amount by the base period percentage for all months during the taxable year preceding the filing month, (iii) determine the tax on the amount determined under clause (ii), and (iv) multiply the tax computed under clause (iii) by the base period percentage for the filing month and all months during the taxable year preceding the filing month. (D) Definitions and special rules For purposes of this paragraph— (i) Base period percentage The base period percentage for any period of months shall be the average percent which the taxable income for the corresponding months in each of the 3 preceding taxable years bears to the taxable income for the 3 preceding taxable years. (ii) Filing month The term “filing month” means the month in which the installment is required to be paid. (iii) Reorganization, etc. The Secretary may by regulations provide for the determination of the base period percentage in the case of reorganizations, new corporations, and other similar circumstances.