Section 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.(4)(a) With respect to a consumer credit transaction, interest after the final scheduled maturity date may not exceed the greater of either 12 percent per year or the annual rate of finance charge assessed on that transaction if the transaction is entered into on or after April 6, 1980 and prior to November 1, 1981, and may not exceed the maximum rate permitted by s. 138.05(1) (a), if the transaction is entered into prior to April 6, 1980, but if such interest is charged no delinquency charge may be taken on the final scheduled installment.(c) With respect to a consumer credit transaction, interest after the final scheduled maturity date shall not exceed the greater of either 12 percent per year or the annual rate of finance charge assessed on that transaction if the transaction is entered into on or after November 1, 1981, but if interest is charged no delinquency charge may be taken on the final scheduled installment.(5) A violation of this section is subject to s. 425.304.1971 c. 239; 1979 c. 10, 168; 1981 c. 45; 1991 a. 39; 1997 a. 302.