California Code, Revenue and Taxation Code - RTC § 23809

(a)(1) The rate of tax specified in Section 1374(b)(1) of the Internal Revenue Code shall be equal to the rate of tax imposed under Section 23151 in lieu of the rate of tax specified in Section 11(b) of the Internal Revenue Code. 1

(2) In the case of an “S” corporation that is also a financial corporation, the rate of tax specified in paragraph (1) shall be increased by the excess of the rate imposed under Section 23183 over the rate imposed under Section 23151.

(d)(1) For corporations described in paragraph (2), the provisions of Sections 1374(c)(1) and 1374(d)(7) of the Internal Revenue Code apply, based upon the effective date of the election to be treated as an “S” corporation for federal tax purposes, regardless of the date on which the corporation became an “S” corporation for state tax purposes.

(2) This subdivision applies to a corporation that, for its last taxable year beginning before January 1, 2002, was an “S” corporation for federal tax purposes and a “C” corporation for purposes of Part 10 (commencing with Section 17001), Part 10.2 (commencing with Section 18401), and this part, and, as a result of the enactment of Chapter 35 of the Statutes of 2002, is an “S” corporation for the corporation's taxable years beginning on or after January 1, 2002.