California Code, Government Code - GOV § 13995.72

If any assessed business that is duly assessed pursuant to this chapter fails to pay to the director the assessed amount by the due date, the director may add to the unpaid assessment an amount not to exceed 10 percent of the unpaid assessment to defray the cost of enforcing the collection of the unpaid assessment. In addition to payment for the cost of enforcing a collection, the assessed business shall pay to the director a penalty equivalent to the lesser of either the maximum amount authorized by Section 1 of Article XV of the California Constitution or 5 percent for each 30 days the assessment is unpaid, prorated over the days unpaid, commencing 30 days after the notice has been given to the assessed business of its failure to pay the assessment on the date required, unless the director determines, to his or her satisfaction, that the failure to pay is due to reasonable cause beyond the control of the assessed business.