Wisconsin Statutes Consumer Transactions (Ch. 421 to 429) § 422.203. Delinquency charges

(1) With respect to a consumer credit transaction other than one pursuant to an open-end credit plan, the parties may agree to a delinquency charge on any installment not paid in full on or before the 10th day after its scheduled or deferred due date in an amount not to exceed $10 or 5 percent of the unpaid amount of the installment, whichever is less.

(2) No delinquency charge may be collected on an installment which is paid in full on or before the 10th day after its scheduled or deferred due date even though an earlier maturing installment or a delinquency charge on an earlier installment may not have been paid in full. For purposes of this subsection payments are applied first to current installments and then to delinquent installments.

(3) A delinquency charge under sub. (1) may be collected only once on an installment however long it remains in default. A delinquency charge may not be collected for a late installment if, with respect to that installment, there has been a deferral.

(5) A violation of this section is subject to s. 425.304.