Cal. Revenue and Taxation Code § 5802

(a) Except as provided in subdivisions (b), (c), and (d), “base year value” as used in this part means the full cash value of a manufactured home on the date the manufactured home is purchased or changes ownership. If the manufactured home undergoes any new construction after it is purchased or changes ownership, the base year value of the new construction is its full cash value on the date on which the new construction is completed, and if uncompleted, on the lien date. (b) The base year value of a manufactured home for which the license fee is delinquent shall be its full cash value on the lien date for the fiscal year in which it is first enrolled. (c) The base year value of a manufactured home converted pursuant to Section 18119 of the Health and Safety Code from taxation under Part 5 (commencing with Section 10701) of Division 2 to taxation under this part shall be its full cash value on the lien date for the fiscal year in which that manufactured home is first enrolled. A manufactured home that has been converted is not subject to supplemental assessment pursuant to Section 75.5 by reason of the conversion. (d) The base year value of a manufactured home that changes ownership in the same calendar year after a conversion in the same calendar year, shall be its full cash value on the date of the change in ownership and its value shall be enrolled on the next lien date. The change in ownership is not subject to supplemental assessment as provided in Section 75.5. (e) This section shall become operative on January 1, 1999.