California Code, Revenue and Taxation Code - RTC § 18536

(a) In lieu of electing nonresident directors filing a return pursuant to Section 18501, the Franchise Tax Board may, pursuant to requirements and conditions set forth in applicable forms and instructions, provide for the filing of a group return by a corporation for one or more electing nonresident individuals who receive wages, salaries, fees, or other compensation from that corporation for director services, including attendance of board of directors' meetings that take place in this state. The tax rate or rates applicable to each director's compensation for services performed in this state shall consist of highest marginal rate or rates provided for by Part 10 (commencing with Section 17001) of Division 2 plus, in the case of any electing nonresident director included on the group return who would be subject to Section 17043 when filing individually, an additional tax rate of 1 percent and no deductions or credits shall be allowed. As required by the Franchise Tax Board, the corporation, as the agent for the electing nonresident directors, shall make the payments of tax, additions to tax, interest, and penalties otherwise required to be paid by, or imposed on, the electing directors.

(b) The Franchise Tax Board may adjust the income of an electing nonresident taxpayer included in a group return filed under this section to properly reflect the income under Part 10 (commencing with Section 17001) of Division 2.