Cal. RTC § 4911.1

(a) If through no fault of the assessee or agent of the assessee a tax payment is credited to property other than the property intended and after a guaranty or certificate of title issues respecting the unintended property, the taxpayer by substantial evidence convinces the tax collector that the payment should have been credited to another property, the tax collector shall transfer the payment in full to the property intended, and shall cancel the credit on the unintended property. In the event a transfer of payment is made, the person owning the unintended property immediately before issuance of the guaranty or certificate of title shall be personally liable for the amount so transferred that shall be collected in the manner specified for the collection of taxes on the unsecured roll.

(b) If any person mistakenly pays an amount of tax on a property after a guaranty of certificate of title has been issued and there is no other property of that person in the county to which that payment properly applies, the tax collector shall, upon being convinced upon substantial evidence that the payment was a mistake, cancel the payment and return the amount paid to that person. Upon cancellation of the payment, the person owning the property immediately before issuance of the guaranty or certificate of title shall be personally liable for the subject tax amount, which shall be collected in the matter specified for the collection of taxes on the unsecured tax roll.