Cal. Unemp. Ins. Code § 456
The director may enter into reciprocal arrangements with authorized agencies of other states or of the Federal Government, or both, whereby employer contributions due under this part with respect to wages for employment shall be deemed to have been paid to the Unemployment Fund of this State as of the date payment of such contributions was made under another state or federal unemployment compensation law. No arrangement shall be entered into pursuant to this section unless it contains provisions for such reimbursement to the fund of such contributions and the actual earnings thereon as the director finds will be fair and reasonable to all affected interests. The director may collect contributions in like manner for such agencies of other states and the Federal Government administering unemployment compensation laws and remit such contributions to such agencies under appropriate reciprocal arrangements.
Ca. Unemp. Ins. Code § 456