California Code, Revenue and Taxation Code - RTC § 7155

(a) Any person who, for the purpose of evading the payment of taxes due under this part, knowingly fails to obtain a valid permit prior to the date on which the first tax return is due shall be liable for a penalty of 50 percent of any tax determined to be due for the period during which the person engaged in business in this state as a seller without a valid permit.

(b) This section shall not apply to any person whose measure of tax liability over the period during which he or she was engaged in business in this state as a seller without a valid permit averaged one thousand dollars ($1,000) or less per month.

(c) This section shall not apply to the amount of taxes due on the sale or use of a vehicle, vessel, or aircraft, if the amount is subject to the penalty imposed by Section 6485.1 or Section 6514.1.