California Code, Financial Code - FIN § 22320.5

(a) A licensee may contract for and receive a delinquency fee not in excess of one of the following amounts:

(b) The delinquency fee may not be collected more than once for the same default and may be collected at the time of the default or at any time thereafter. If the delinquency fee is deducted from any payment received after default occurs, and the deduction results in the default of a subsequent installment, no fee may be collected for the resulting default. The delinquency fee under this section is not included in charges defined in this division or in determining applicable maximum charges that may be made under this article.

(c) For open-end loans made under Article 5 (commencing with Section 22450), a licensee shall not collect or receive the delinquency fee set forth in subdivision (a) unless there is a minimum of 20 days, inclusive, between the monthly billing date and the date upon which the minimum payment is due, exclusive of the applicable grace period provided in subdivision (a).

(d) This section shall not apply to precomputed loans as described in Section 22400.