Gov. Code, § 66499.20.1

A city or county may, by ordinance, authorize a parcel map to be filed under the provisions of this chapter for the purpose of reverting to acreage land previously subdivided and consisting of four or less contiguous parcels under the same ownership. Any map so submitted shall be accompanied by evidence of title and nonuse or lack of necessity of any public streets or public easements which are to be vacated or abandoned. Any public streets or public easements to be left in effect after the reversion shall be adequately delineated on the map. After approval of the reversion by the governing body or advisory agency the map shall be delivered to the county recorder. The filing of the map shall constitute legal reversion to acreage of the land affected thereby, and shall also constitute abandonment of all public streets or public easements not shown on the map, provided however that written notation of each abandonment is listed by reference to the recording data creating those public streets or public easements and certified to on the map by the clerk of the legislative body or the designee of the legislative body approving the map. The filing of the map shall also constitute a merger of the separate parcels into one parcel for purposes of this chapter and shall thereafter be shown as such on the assessment roll subject to the provisions of Section 66445. Except as provided in subdivision (f) of Section 66445, on any parcel map used for reverting acreage, a certificate shall appear signed and acknowledged by all parties having any record title interest in the land being reverted, consenting to the preparation and filing of the parcel map.