California Code, Revenue and Taxation Code - RTC § 20512

(a) “Property taxes accrued” means current property taxes (exclusive of interest, penalties, principal payments on improvement bonds and charges for service) levied against a claimant's residential dwelling by any taxing agency (as defined in Section 121) for any fiscal year ending on or after June 30, 1977. If the owner of a dwelling unit which is a mobilehome located on land owned or rented by such owner pursuant to Section 20541 elects to claim assistance under Section 20543, such assistance shall be based on the appropriate percentage of the motor vehicle license fee tax, not including the registration fee, paid with regard to such mobilehome.

(b) Whenever a residential dwelling is an integral part of a large unit such as a farm, or a multipurpose or multidwelling building, “property taxes accrued” shall be that percentage of the total property taxes accrued as the value of the residential dwelling is of the total value.

(c) Where a claimant is purchasing the residential dwelling under an unrecorded contract of sale, the Franchise Tax Board may require a copy of the contract or other evidence to establish such fact.

(d) Where the residential dwelling is a dwelling owned by the claimant on land owned by a nonprofit incorporated association, the Franchise Tax Board may require an affidavit under penalty of perjury containing sufficient evidence to establish such fact and that the nonprofit incorporated association requires that the claimant pay a pro rata share of the property tax levied against the association's land.

(e) Where the residential dwelling consists of premises occupied by reason of the claimant's possessory interest in such premises, the Franchise Tax Board may require an affidavit under penalty of perjury stating that the premises are occupied by reason of ownership of a possessory interest in a dwelling that is otherwise exempt from property taxation.