CA Civ Code Section 1805.4

The finance charge shall be inclusive of all charges incident to investigating and making the contract and for the extension of the credit provided for in the contract, and no fee, expense or other charge whatsoever shall be taken, received, reserved or contracted for except as otherwise provided in this chapter. The seller or holder of a retail installment contract 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 contract. 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.