If the income of two or more taxpayers is derived solely from sources within this state and their business activities are such that if conducted within and without this state a combined report would be required to determine their business income derived from sources within this state, then such taxpayers shall be allowed to determine their business income in accordance with Section 25101.
(Added by Stats. 1980, Ch. 390, Sec. 1. Effective July 10, 1980. Applicable to income years beginning on or after January 1, 1980, by Sec. 2 of Ch. 390.)