Cal. Gov. Code § 20031

“Employer federal contributions” means those contributions required of employers under the federal system with respect to wages paid to individuals who perform services in employment in any coverage group included in the federal-state agreement, at the rate of taxes imposed on employers by Section 3111 of Title 26 of the United States Code for the respective calendar years set forth therein and all penalties and interest that may be required to be paid with respect to those wages under the federal-state agreement.