California Code, Civil Code - CIV § 1812.626

(a) The lessor may assess a late payment fee if the late payment fee is specified in the rental-purchase agreement and is permitted by this section.

(b) No fee shall be assessed for a payment which is less than three days late if the rental-purchase agreement specifies weekly periodic payments.

(c) No fee shall be assessed for a payment which is less than 7 days late if the rental-purchase agreement specifies longer than weekly periodic payments.

(d) The lessor may assess more than one late fee for a particular late payment if the total of all fees assessed for that late payment does not exceed the maximum provided in subdivision (e). If the maximum total late payment fee has been imposed for a particular payment, no additional late payment fee may be imposed for that payment.

(e) The total of all fees for a late payment shall not exceed the lesser of 5 percent of the payment or five dollars ($5), except that a minimum total fee of two dollars ($2) may be required.