Cal. Civ. Code § 1810.4
The finance charge shall include all charges incident to investigating and making the retail installment account. No fee, expense, delinquency, collection, or other charge whatsoever shall be taken, received, reserved, or contracted by the seller or holder of a retail installment account except as provided in this section. A seller may, however, in an agreement which is accepted by the buyer and of which a copy is given or furnished to the buyer provide for the payment of attorney's fees and costs in conformity with Article 11 (commencing with Section 1811.1). Any subsequent change in any term of the agreement shall not become effective until the seller has given notice of the change and complies with the provisions of subdivision (d) of Section 1810.3. When credit cards are issued in connection with a retail installment account, the seller, either in the agreement or after giving the notice required by subdivision (d) of Section 1810.3, may require the payment of an annual fee of not more than fifteen dollars ($15) for membership in the credit card plan, which fee shall not be deemed a finance charge or interest for any purpose of the law.
The seller or holder of a retail installment account may charge and collect a fee not to exceed fifteen dollars ($15) for the return by a depository institution of a dishonored check, negotiable order of withdrawal, or share draft issued in connection with the retail installment account. The fee is not included in charges as defined in this chapter or in determining the applicable charges which may be made under this chapter.
Ca. Civ. Code § 1810.4