California Code, Revenue and Taxation Code - RTC § 38451

(a) Subject to subdivision (c), a person who fails to pay any tax to the state or any amount of tax required to be collected and paid to the state, except amounts of determinations made by the California Department of Tax and Fee Administration under Articles 2 or 3  1 of this chapter, within the time required shall pay a penalty of 10 percent of the tax or amount of the tax, in addition to the tax or the amount of tax, plus interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5 from the date on which the tax or the amount of tax required to be collected became due and payable to the state until the date of payment.

(b) Subject to subdivision (c), a person who fails to file a return in accordance with the due date set forth in Section 38401 or the due date established by the California Department of Tax and Fee Administration in accordance with Section 38404, shall pay a penalty of one hundred dollars ($100).

(c) A person who is liable for the penalties described in this section shall pay either the penalty described in subdivision (a) or the penalty described in subdivision (b), whichever is greater.