Cal. Unemp. Ins. Code § 3702
Extended duration benefits, to the extent that such extended duration benefits are not reimbursed or reimbursable by the federal government to the State of California, shall be charged except as provided by Section 1032, 1032.5, 1034, 1036, 1335, 1338, or 1380, against the reserve account of the exhaustee's employer during his or her base period. If the individual performed services in employment for more than one employer during his or her base period, unemployment compensation benefits paid to him or her shall be charged against the respective reserve accounts of such employers in the proportion that the total wages paid to the individual in employment for each employer bears to the total wages paid to the individual in employment for all employers during the base period.
Ca. Unemp. Ins. Code § 3702