California Code, Water Code - WAT § 72072.7

(a) Any service supplier who fails to remit any tax imposed by this article within 30 days after receipt of written notice from the board of such failure shall pay a penalty of 10 percent of the amount of the tax.

(b) If the board determines that the nonpayment of any remittance due under this article is due to fraud, a penalty of 25 percent of the amount of the tax shall be added thereto in addition to the penalty stated in subdivision (a).

(c) In addition to the penalties imposed in this section, any service supplier who fails to remit any tax imposed by this part, shall pay interest at the rate of 1 percent per month, or fraction thereof, on the amount of the tax exclusive of penalties, from the date on which the remittance first became delinquent until paid.