California Code, Revenue and Taxation Code - RTC § 72

(a) A copy of any building permit issued by any city, county, city and county, or any entity authorized to issue a building permit shall be transmitted by each issuing entity to the county assessor as soon as possible after the date of issuance.

(b) A copy of any certificate of occupancy or other document that shows the date of completion of new construction issued or finalized by any city, county, city and county, or any entity authorized to issue a building permit, shall be transmitted by each entity to the county assessor within 30 days after the date of issuance or finalization.

(c) At the time an assessee files, or causes to be filed, an approved set of building plans with the issuing entity a scale copy of the floor plans and exterior dimensions of the building designated for the county assessor shall be filed by the assessee or the assessee's designee. The scale copy shall be in sufficient detail to allow the assessor to determine the square footage of the building and, in the case of a residential building, the intended use of each room. The county assessor may require the floor plans be provided to the county assessor in an electronic format, if available. An assessee, or the assessee's designee, where multiple units are to be constructed from the same set of building plans, may file only one scale copy of floor plans and exterior dimensions, so long as each application for a building permit with respect to those building plans specifically identifies the scale copy filed pursuant to this section. However, where the square footage of any one of the multiple units is altered, an assessee, or the assessee's designee, shall file a scale copy of the floor plan and exterior dimensions that specifically identifies the alteration from the previously filed scale copy. The receiving authority shall transmit that copy to the county assessor as soon as possible after the final plans are approved.

(d) The board of supervisors of a county may enact, by a majority vote of its entire membership, an ordinance, resolution, or board order that requires the local agency that approves the tentative map or maps, and any conditions of approval for the tentative map or maps that are filed with a county or a city in that county, to submit a copy of the map or maps, and any conditions of approval for the tentative map or maps, to the county assessor as soon as possible after the map or maps are filed. The ordinance, resolution, or board order may require that the map or maps be provided to the county assessor in an electronic format, if available in that form.