Cal. CIV § 1812.637

(a) A lessor is not liable for a violation of this title if, before the 30th calendar day after the date the lessor discovers a bona fide error and before an action under this title is filed or written notice of the error is received by the lessor from the consumer, the lessor gives the consumer written notice of the error. “Bona fide error,” as used in this section, means a violation that was not intentional and resulted from a bona fide error notwithstanding the maintenance of procedures reasonably adapted to avoid that error. Examples of a bona fide error include clerical errors, calculation errors, errors due to unintentionally improper computer programming or data entry, and printing errors, but does not include an error of legal judgment with respect to a lessor’s obligations under this title.

(b) Notwithstanding subdivision (a), if the lessor notifies the consumer of a bona fide error the correction of which would increase the amount of any payment, the lessor may not collect the amount of the increase, and the consumer may enforce the rental-purchase agreement as initially written.

(c) Notwithstanding subdivision (a), if the lessor notifies the consumer of a bona fide error the correction of which would lower the amount of any payment, the lessor shall immediately refund to the consumer the difference between what the consumer paid and what the consumer should have paid if the agreement were correct at the inception of the transaction.