RTC §8876: (a) Any user who fails to pay any tax, except taxes determined by the board under Article 2 (commencing with Section 8776) or Article 3 (commencing with Section 8801), within the time required shall p

(a) Any user who fails to pay any tax, except taxes determined by the board under Article 2 (commencing with Section 8776) or Article 3 (commencing with Section 8801), within the time required shall pay a penalty of 10 percent of the amount of the tax, together with interest on that tax at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the date on which the tax became due and payable until the date of payment. (b) Any user who fails to file a return in accordance with the due date set forth in Section 8751 or the due date established by the board in accordance with Section 8755, shall pay a penalty of 10 percent of the amount of the tax with respect to the period for which the return is required. (c) The penalties imposed by this section shall be limited to a maximum of 10 percent of the tax for which the return is required for any one return.