Cal. Public Resources Code § 3420

(a) (1) No charges shall be levied for assessments on oil and gas production of less than ten dollars ($10). (2) The charges levied for assessments are due and payable on the first of July in each year for assessments of more than ten dollars ($10), but less than five hundred dollars ($500). The charges shall be delinquent if not paid on or before August 15th of each year. (3) The charges levied for assessments are due and payable on the first of July in each year for assessments of five hundred dollars ($500) or more. One-half of the charges shall be delinquent if not paid on or before August 15th of each year. The remaining one-half of the charges shall be delinquent if not paid on or before the first of February of the following year. (b) Idle well fee charges pursuant to Section 3206 are due and payable as specified pursuant to that section and are immediately delinquent if not paid as required. (c) Charges to an operator pursuant to Section 3226 for actual or estimated costs to perform work ordered are delinquent if not paid within 30 days after service of the accounting of costs. (d) Any person who fails to pay any charge within the time required shall pay a penalty of 10 percent of the amount due, plus interest at the rate of 112 percent per month, or fraction thereof, computed from the delinquent date of the assessment, idle well fee, or other charge pursuant to this chapter until and including the date of payment.