Cal. Food & Agric. Code § 35312

To the amount of any fee, except a license fee, which is required by this division, that is not paid by the last day of the month following that in which due, there shall be added a penalty of 25 percent of the unpaid amount of such fee, or five dollars ($5), whichever is greater, for each month or fraction of a month until the entire fee and penalty are paid.