Unemp. Ins. Code, § 13028.5

(a) For purposes of this division (and so much of Part 10 (commencing with Section 17001) and Part 10.2 (commencing with Section 18401) of Division 2 of the Revenue and Taxation Code as relates to this division) any supplemental unemployment compensation benefit paid to an individual shall be treated as if it were a payment of wages by an employer to an employee for a payroll period.

(b) For purposes of subdivision (a), “supplemental unemployment compensation benefits” means amounts which are paid to an employee, pursuant to a plan to which the employer is a party, because of an employee’s involuntary separation from employment (whether or not that separation is temporary), resulting directly from a reduction in force, the discontinuance of a plant or operation, or other similar conditions, but only to the extent those benefits are includable in the employee’s gross income.