California Code, Government Code - GOV § 16183

(a) From the time a payment is made pursuant to Section 16180, the amount of that payment shall bear interest at a rate (not compounded), determined as follows:

(b) The interest provided for in subdivision (a) shall be applied beginning the first day of the month following the month in which that payment is made and continuing on the first day of each month thereafter until that amount is paid. In the event that any payments are applied, in any month, to reduce the amount paid pursuant to Section 16180, the interest provided for herein shall be applied to the balance of that amount beginning on the first day of the following month.

(c) In computing interest in accordance with this section, fractions of a cent shall be disregarded.

(d) For the purpose of this section, the time a payment is made shall be deemed to be the time a payment is made by the Controller to the tax collector or the delinquency date of the respective tax installment, whichever is later.

(e) The Controller shall include on forms supplied to claimants pursuant to Sections 20621, 20630.5, 20639.9, 20640.9, and 20641 of the Revenue and Taxation Code, a statement of the interest rate which shall apply to amounts postponed for the fiscal year to which the form applies.