California Code, Revenue and Taxation Code - RTC § 2610.6

When the tax collector sends a tax bill to any person respecting property which has been assessed to another and who has the power, pursuant to written or oral authorization, to pay the taxes on behalf of another, the tax collector shall send to the assessee an information copy of the tax bill, except, that the copy shall state plainly that the copy is not a bill and that the original bill has been sent to another person for payment.