When a county boundary is changed pursuant to this article, the boards of supervisors of the affected counties shall file before the following December 1, with the State Board of Equalization and with the assessors of the affected counties, a statement setting forth the legal description of the boundary, as changed, together with a map or plat indicating the boundary. The change of the boundary shall not be effective for purposes of assessment or taxation unless the statement, together with the map or plat is filed with the assessors and the State Board of Equalization on or before December 1 of the year immediately preceding the year in which the assessments or taxes are to be levied.
Ca. Gov. Code § 23212