(1) Notwithstanding any prior election made with respect to consolidated returns, and subject to subsection (5), for taxable years beginning on or after September 1, 1984, any corporation subject to tax under this code which corporation is the parent company of an affiliated group of corporations may elect, not later than the due date for filing its return for the taxable year, including any extensions thereof, to consolidate its taxable income with that of all other members of the group, regardless of whether such member is subject to tax under this code, and to return such consolidated taxable income hereunder, in which case all such other members must consent thereto in such manner as the department may by rule prescribe, provided:(a) Each member of the group consents to such filing by specific written authorization at the time the consolidated return is filed;
(b) The affiliated group so filing under this code has filed a consolidated return for federal income tax purposes for the same taxable year; and
(c) The affiliated group so filing under this code is composed of the identical component members as those which have consolidated their taxable incomes in such federal return.
(2) Subject to subsection (5), the director may require a consolidated return for those members of an affiliated group of corporations which are subject to tax and which would be eligible to elect to consolidate their incomes under subsection (1), if the filing of separate returns for such corporations would improperly reflect the taxable incomes of such corporations or of such group.
(3) The filing of a consolidated return for any taxable year shall require the filing of consolidated returns for all subsequent taxable years so long as the filing taxpayers remain members of the affiliated group or, in the case of a group having component members not subject to tax under this code, so long as a consolidated return is filed by such group for federal income tax purposes, unless the director consents to the filing of separate returns.
(4) The computation of consolidated taxable income for the members of an affiliated group of corporations subject to tax hereunder shall be made in the same manner and under the same procedures, including all intercompany adjustments and eliminations, as are required for consolidating the incomes of affiliated corporations for the taxable year for federal income tax purposes in accordance with s. 1502 of the Internal Revenue Code, and the amount shown as consolidated taxable income shall be the amount subject to tax under this code.
(5) Each taxpayer shall apportion adjusted federal income under s. 220.15 as a member of an affiliated group which files a consolidated return under this section on the basis of apportionment factors described in s. 220.15. For the purposes of this subsection, each special industry member included in an affiliated group filing a consolidated return, who would otherwise be permitted to use a special method of apportionment under s. 220.151 or s. 220.153, shall construct the numerator of its sales, property, and payroll factors, respectively, by multiplying the denominator of each such factor by the premiums, revenue miles, or single sales factor ratio otherwise applicable under s. 220.151 or s. 220.153 in the manner prescribed by department rule. 
