Cal. Unemp. Ins. Code § 1110.6
Notwithstanding the provisions of Section 1110, whenever the liability of an employer for contributions under this division arises under the terms of a written contract in which such employer has agreed, for the benefit of another party to such contract, to assume ultimate liability for contributions under this division in the event of the default in payment thereof by any other employer affected by such contract, such contributions shall not become delinquent and no penalties or interest prescribed by this chapter shall commence to accrue with respect to such contracting employer, until after the 30th day following the date of mailing or service of notice upon him, by the director, of the default of any such other employer.
Ca. Unemp. Ins. Code § 1110.6