Cal. Elec. Code § 2122
The county elections official may cause to be written or printed upon the top margin, or in the body of the affidavit, in addition to any matter provided for in this code, any words necessary or convenient to designate the precinct, district, or political subdivision for which the affidavit is taken, or to indicate any removal or transfer of registration. Any other reasonable memoranda may be added that is necessary or convenient to enable the county elections official to perform his or her duties in assorting or classifying or handling affidavits with correctness and dispatch. However, the memoranda shall not include notations, whether coded or not, that indicate that the registrant has signed a particular initiative, referendum, or recall petition unless the notations are made other than on the body of the affidavit of registration. Any memoranda, notations, devices, computer data, or other means or material employed by the elections official indicating which petition or petitions have been signed by any registrant shall be destroyed as soon as practicable after the certification of the results of the election for which the memoranda, notations, devices, computer data, or other means or material was used, or if no election is held, as soon as practicable after the final certification of the elections official showing the results of the examination of the petition. In no event shall the memoranda, notations, devices, computer data, or other means or material be retained for more than 30 days.
The memoranda, notations, devices, computer data, or other means or material employed by the elections official indicating which petition or petitions have been signed by any registrant shall be available for the use of the elections official and his or her staff only and then only for the purposes for which they were prepared. Except as previously provided, they shall not be made available to any person or entity, public or private, for any purpose whatsoever.
Memoranda added to the body of the affidavit of registration, which are not applicable to the requirements of Section 2150, shall not be deemed a portion of the affidavit.
Ca. Elec. Code § 2122