If a payment is more than a month late, use the Monthly Compounding Interest Calculator. If a payment is less than 31 days late, use the Simple Daily Interest Calculator. To use this calculator you must enter the numbers of days late, the amount of the invoice in which payment was made late, and the Prompt Payment interest rate, which is pre-populated in the box. The following on-line calculator allows you to automatically determine the amount of simple daily interest owed on payments made after the payment due date. Please enable JavaScript to use all features. Some features of this site will not work with JavaScript disabled.
