California Code, Revenue and Taxation Code - RTC § 11911.1

Any ordinance which imposes the documentary transfer tax may require that each deed, instrument or writing by which lands, tenements, or other realty is sold, granted, assigned, transferred, or otherwise conveyed, shall have noted upon it the tax roll parcel number. The number will be used only for administrative and procedural purposes and will not be proof of title and in the event of any conflicts, the stated legal description noted upon the document shall govern. The validity of such a document shall not be affected by the fact that such parcel number is erroneous or omitted, and there shall be no liability attaching to any person for an error in such number or for omission of such number.