California Code, Unemployment Insurance Code - UIC § 1135

(a) Assessments under this article become delinquent if not paid on or before the date they become final pursuant to Sections 1036, 1221, 1222, and 1224. There shall be added to the amount of each delinquent assessment a penalty of 15 percent of the amount thereof exclusive of interest and penalties.

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