Cal. RTC § 19023

For purposes of this article, in the case of a corporation or an organization described in Section 23731, the term “estimated tax” means the amount which the corporation or organization described in Section 23731 estimates as the amount of the tax imposed by Part 11 (commencing with Section 23001) and the amount of its liability for the tax of each wholly owned subsidiary under Section 23800.5; but in no event shall the estimated tax of a corporation subject to the tax imposed by Article 2 (commencing with Section 23151) of Chapter 2 of Part 11 be less than the minimum tax prescribed in Section 23153.