California Code, Revenue and Taxation Code - RTC § 20509

(a) Premises which are exempt from property taxation, except those premises on which the owner pays possessory interest taxes, or makes payments in lieu of property taxes which are substantially equivalent to property taxes paid on properties of comparable market value.

(b) Premises which are not located in this state.

For the purposes of this section, the term “premises” means a house or a dwelling unit used to provide living accommodations in a building or structure and the land incidental thereto, but does not include land only, except in the case where the dwelling unit is a mobilehome subject to the license fee imposed by Part 5 (commencing with Section 10701) of this division.  “Rented residence” includes a dwelling unit which is a mobilehome subject to the license fee imposed by Part 5 (commencing with Section 10701) of this division owned by the claimant and located on land which is owned or rented by such claimant.