Cal. Revenue and Taxation Code § 43154

(a) Except as provided in subdivision (b), the board for good cause may extend, for a period of time not to exceed one month, the time for making any return or paying any amount required to be paid under this part. The extension may be granted at any time provided a request therefor is filed with the board within or prior to the period for which the extension may be granted. (b) (1) In the case of a disaster, the board, for a period not to exceed three months, may extend the time for making any report or return or paying any tax required under this part. The extension may be granted at any time provided a request therefor is filed with the board within or before the period for which the extension may be granted. (2) For purposes of this section, “disaster” means fire, flood, storm, tidal wave, earthquake, or similar public calamity, whether or not resulting from natural causes. (c) Any person to whom an extension is granted shall pay, in addition to the tax, interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the date on which the tax would have been due without the extension until the date of payment.