If 22.5 percent for the first installment, 45 percent for the 2nd installment, 67.5 percent for the 3rd installment and 90 percent for the 4th installment of the tax for the taxable year computed by annualizing, under methods prescribed by the department of revenue, the corporation’s income, or the virtually exempt entity’s unrelated business taxable income, for the months in the taxable year ending before the installment’s due date is less than the installment required under par. (a), the corporation or virtually exempt entity may pay the amount under this paragraph rather than the amount under par. (a). For purposes of computing annualized income under this paragraph, the apportionment percentage computed under s. 71.25 (6) and (10) to (12) from the return filed for the previous taxable year may be used if that return is filed with the department of revenue on or before the due date of the installment for which the income is being annualized and the apportionment percentage on that previous year’s return is greater than zero or may be used if that return is filed with the department of revenue on or before the due date of the 3rd installment, the apportionment percentage on that previous year’s return is greater than zero and the apportionment percentage used in the computation of the first 2 installments is not less than the apportionment percentage on that previous year’s return. For purposes of computing annualized income of corporations that are subject to a tax under this chapter on unrelated business taxable income, as defined under section 512 of the internal revenue code, and virtually exempt entities, the taxpayer’s income for the months in the taxable year ending before the date one month before the due date for the installment shall be used. Any corporation or virtually exempt entity that pays an amount calculated under this paragraph shall increase the next installment computed under par. (a) by an amount equal to the difference between the amount paid under this paragraph and the amount that would have been paid under par. (a).