California Code, Unemployment Insurance Code - UIC § 1127

(a) If the director is not satisfied with any return or report made by any employing unit of the amount of employer or worker contributions, he or she may compute the amount required to be paid upon the basis of facts contained in the return or reports or may make an estimate upon the basis of any information in his or her possession or that may come into his or her possession and make an assessment of the amount of the deficiency. If any part of the deficiency is due to negligence or intentional disregard of this division or authorized regulations, a penalty of 15 percent of the amount of the deficiency shall be added to the assessment.

(b) The changes made to this section by the act adding this subdivision  1 shall apply on and after July 1, 2014.