Rev. & Tax. Code, § 6244

(a) If a purchaser who gives a resale certificate or purchases property for the purpose of reselling it makes any storage or use of the property other than retention, demonstration, or display while holding it for sale in the regular course of business, the storage or use is taxable as of the time the property is first so stored or used.

(b) If such use is limited to the loan of the property to customers as an accommodation while awaiting delivery of property purchased or leased from the lender or while property is being repaired for customers by the lender, the measure of the tax is the fair rental value of the property for the duration of each loan so made.

(c) If the property is used frequently for purposes of demonstration or display while holding it for sale in the regular course of business and is used partly for other purposes, the measure of the tax is the fair rental value of the property for the period of such other use or uses.

(d) If the property is mobile transportation equipment as defined in Section 6023, and the use is limited to leasing the equipment, the purchaser may elect to pay his use tax measured by the fair rental value, if the election is made on or before the due date of a return for the period in which the equipment is first leased. The election must be made by reporting tax measured by the fair rental value on the return for that period, or in such other manner as the board may prescribe. Tax must thereafter be paid with the return for each reporting period, measured by the fair rental value, whether the equipment is within or without the state. The election may not be revoked with respect to the equipment as to which it is made.

(e) As used in subdivision (d), the term “fair rental value” means the rentals required by the purchaser under the lease except where the board determines that such rentals are nominal. The term shall not include any reimbursement payments made by the lessee to the purchaser for such use tax.