(a) Sections 63-3027B through 63-3027E, Idaho Code, shall be operative for the computation of taxes for the earlier of either of the following:
(1)  Taxable years beginning on or after January 1, 1988.
(2)  Taxable years beginning on or after January 1 of the year after the year in which the board of examiners, upon advice of the attorney general, certifies to the tax commission that action has been taken by the United States, whether by statute, regulation, executive order, or any other means as may be appropriate, to comply substantially with the following:
(A)  A requirement that any corporation required to file a United States tax return or which could be included in a consolidated federal tax return be required to file with the Internal Revenue Service a domestic disclosure spreadsheet if its payroll, property, or sales in a foreign country exceeds one million dollars ($1,000,000). The spreadsheet shall provide for full disclosure as to the income reported to each state, the state tax liability, and the method used for apportioning or allocating income to the states, and any other information as provided for by regulations as may be necessary to determine properly the amount of taxes due to each state and to identify the water’s-edge corporate group and those of its affiliates of which more than twenty per cent (20%) of the voting stock is directly or indirectly owned or controlled by a common owner or owners.
(B)  That the information filed pursuant to paragraph (2)(A) of this subsection will be available to qualified states. A "qualified state" is any state that does not require the use of the worldwide unitary method of taxation except in circumstances substantially similar to those authorized in subsection (c) of section 63-3027B, Idaho Code.
(C)  That qualified states are authorized access to all material developed by the Internal Revenue Service in its examination of multinational operations.
(b)  If sections 63-3027B through 63-3027E, Idaho Code, become operative pursuant to paragraph (1) of subsection (a) of this section, the tax commission may require, and taxpayers described in this subsection must file, no later than six months after filing the Idaho income tax return, a spreadsheet to provide disclosure as to the income reported for the year to the other states that require unitary combined reporting, the tax liability for each such state, the method used for allocating or apportioning income to such states, the property, payroll, and destination sales of the water’s-edge corporate group in each state, and to identify the water’s-edge corporate group and those of its affiliates of which more than twenty per cent (20%) of the voting stock is directly or indirectly owned or controlled by a common owner or owners. The provisions of this subsection shall apply only to corporations which both make a water’s-edge election and have during the taxable year, payroll, property or sales in a foreign country which exceeds one million dollars ($1,000,000). Notwithstanding the requirement to file a spreadsheet in any tax year, a taxpayer may forego filing such a spreadsheet by submitting to the state tax commission a written declaration of its intention to forego filing such spreadsheet for such year. In the event such declaration is filed in any tax year, no spreadsheet shall be required of such taxpayer and the percentage to be applied under section 63-3027C(c)(3) for such year shall be eighty per cent (80%) rather than eighty-five per cent (85%).