Taxable income
(B) Taxable income means the positive taxable income of a component member for its entire tax year (even if it was not a member of the group for each day of that tax year) that includes the same December 31st testing date, which is also applicable to the other component members of that same controlled group. (2) Apportionment(i) General rule. Any additional tax determined under paragraph (a)(1) of this section shall be apportioned among such members in the same manner as the corresponding tax bracket of section 11(b)(1) is apportioned. For rules to apportion the section 11(b)(1) tax brackets among the component members of a controlled group, see 1.1561-3(b) or (c). (ii) Apportionment methods. Unless the component members of a controlled group elect to use the first-in-first-out (FIFO) method described in paragraph (a)(2)(ii)(B) of this section, such members are required to apportion the amount of the additional tax using the proportionate method described in paragraph (a)(2)(ii)(A) of this section. These component members may elect the FIFO method by specifically adopting such method in their apportionment plan. (A) Proportionate method. Under the proportionate method, the additional tax is allocated to each component member in the same proportion as the portion of the tax-benefit amount that inured to a member from utilizing lower tax brackets bears to the amount of the group's total tax-benefit amount inuring to it from utilizing those lower tax brackets. The tax-benefit amount that inures to a corporation from using a particular tax bracket is the tax savings that such corporation realizes from having a portion of its taxable income taxed at the lower rate attributed to that tax bracket instead of the high tax rates to which it would otherwise be subject. The steps for applying the proportionate method of allocation are as follows: