Except as provided in par. (d), if 80 percent or more of a corporation’s worldwide income is active foreign business income, the income and apportionment factor or factors of the corporation shall not be included in the combined report, but the corporation shall compute and allocate or apportion its income from the unitary business separately.

For purposes of subd. 1., “active foreign business income” means gross income derived from sources outside the United States, as determined in subchapter N of the Internal Revenue Code, including income of a subsidiary corporation, and attributable to the active conduct of a trade or business in a foreign country or in a U.S. possession.

For purposes of subd. 2., a corporation is considered a subsidiary if the parent corporation owns, directly or indirectly, stock with at least 50 percent of the total voting power of the corporation and the stock has a value equal to at least 50 percent of the total value of the stock of the corporation.