Cal. RTC § 12287

Except for the retaliatory tax due on ocean marine insurance, the retaliatory tax shall be due and payable on or before April 1 and shall be paid by remittance made payable to the Controller. Any additional retaliatory tax due on account of ocean marine insurance shall be due and payable on or before June 15 and shall be paid by remittance made payable to the Controller. If not paid on or before the due date, the amount of retaliatory tax shall bear interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from April 1 (June 15 with respect to any additional ocean marine retaliatory tax) until the date of payment, and there shall be paid in addition to the tax and interest, a penalty of 10 percent of the amount of the retaliatory tax.