California Code, Revenue and Taxation Code - RTC § 23301

(a) If any tax, penalty, or interest, or any portion thereof, that is due and payable under Chapter 4 (commencing with Section 19001) of Part 10.2, or under this part, either at the time the return is required to be filed or on or before the 15th day of the 9th month following the close of the taxable year, is not paid on or before 6 p.m. on the last day of the 12th month after the close of the taxable year.

(b) If any tax, penalty, or interest, or any portion thereof, due and payable under Chapter 4 (commencing with Section 19001) of Part 10.2, or under this part, upon notice and demand from the Franchise Tax Board, is not paid on or before 6 p.m. on the last day of the 11th month following the due date of the tax.

(c) If any liability, or any portion thereof, which is due and payable under Article 7 (commencing with Section 19131) of Chapter 4 of Part 10.2, is not paid on or before 6 p.m. on the last day of the 11th month following the date that the tax liability is due and payable.