Cal. Unemp. Ins. Code § 13030
If wages are paid with respect to a period which is not a payroll period, the amount to be deducted and withheld shall be that applicable in the case of a miscellaneous payroll period containing a number of days, including Sundays and holidays, equal to the number of days in the period with respect to which such wages are paid. In any case in which wages are paid by an employer without regard to any payroll period or other period, the amount to be deducted and withheld shall be that applicable in the case of a miscellaneous payroll period containing a number of days equal to the number of days, including Sundays and holidays, which have elapsed since the date of the last payment of such wages by such employer during the calendar year, or the date of commencement of employment with such employer during such year, or January 1st of such year, whichever is the later. In any case in which the period of time described, or the time prescribed in the preceding sentence in respect of any wages, is less than one week, the department may by authorized regulation permit an employer, in computing the tax required to be deducted and withheld, to use the excess of the aggregate of the wages paid to the employee during the calendar week over the withholding exemption allowed by Section 13020 for a weekly payroll period.
Ca. Unemp. Ins. Code § 13030