California Code, Government Code - GOV § 51549

As soon as practicable after the lien date following the effective date of the charter provision or ordinance, the city clerk shall deliver to the county assessor a written statement showing separately the exterior boundaries of the city as originally incorporated and the exterior boundaries of each body of new territory subsequently added and the date of addition. Thereafter, any changes in the city's boundaries shall be reported to the county assessor and the State Board of Equalization under the provisions of Sections 54900 to 54903, inclusive.