California Code, Revenue and Taxation Code - RTC § 6480.4

(a) Any supplier or wholesaler who fails to make a timely remittance to the board of the prepayment amounts, if any, required pursuant to Sections 6480.1 and 6480.3 shall also pay a penalty of 10 percent of the amount of the prepayment due but not paid, plus interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the date the prepayment became due and payable to the state until the date of payment.

(b) The penalty amount specified in subdivision (a) shall be 25 percent if the supplier or wholesaler knowingly or intentionally fails to make a timely remittance.