Cal. Rev. & Tax. Code § 25110
(a) Notwithstanding Section 25101, a qualified taxpayer, as defined in paragraph (2) of subdivision (b), that is subject to the tax imposed under this part, may elect to determine its income derived from or attributable to sources within this state pursuant to a water’s-edge election in accordance with the provisions of this part, as modified by this article. A taxpayer, that makes a water’s-edge election on or after January 1, 2006, shall take into account that portion of its own income and apportionment factors and the income and apportionment factors of its affiliated entities to the extent provided below:
(1) The entire income and apportionment factors of any of the following corporations:
(2)
(A) With respect to a corporation that is not described in subparagraphs (A), (B), (C), and (D) of paragraph (1), as provided in either one or both of the following clauses:
(B) For purposes of this paragraph, both of the following apply:
(b) For purposes of this article and Section 24411, all of the following definitions apply:
(2) A “qualified taxpayer” means a corporation that does both of the following:
(B) Agrees that, for purposes of this article, dividends received by any corporation whose income and apportionment factors are taken into account pursuant to subdivision (a) from either of the following are functionally related dividends and shall be presumed to be business income:
(ii) Any corporation that is either a significant source of supply for the unitary business or a significant purchaser of the output of the unitary business, or that sells a significant part of its output or obtains a significant part of its raw materials or input from the unitary business. “Significant,” as used in this subparagraph, means an amount of 15 percent or more of either input or output.
All other dividends shall be classified as business or nonbusiness income without regard to this subparagraph.
(3) The definitions and locations of property, payroll, and sales shall be determined under the laws and regulations that set forth the apportionment formulas used by the individual states to assign net income subject to taxes on, or measured by, net income in that state. If a state does not impose a tax on, or measured by, net income or does not have laws or regulations with respect to the assignment of property, payroll, and sales, the laws and regulations provided in Article 2 (commencing with Section 25120) shall apply.
Sales shall be considered to be made to a state only if the corporation making the sale may otherwise be subject to a tax on, or measured by, net income under the Constitution or laws of the United States, and shall not include sales made to a corporation whose income and apportionment factors are taken into account pursuant to subdivision (a) in determining the amount of income of the taxpayer derived from or attributable to sources within this state.