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Monthly Compounding Interest Calculator

The following on-line calculator allows you to automatically determine the amount of monthly compounding interest owed on payments made after the payment due date. To use this calculator you must enter the numbers of days late, the number of months 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. If your payment is only 30 days late or less, please use the simple daily interest calculator.

Please do not enter commas.

Enter the principal amount:
Enter the number of months late:

Enter the number of days late:
Enter 0 through 31. This number is NOT the total number of days late

Enter the Prompt Payment interest rate:

You owe the vendor $ in interest.
Your total payment to the vendor is $


   Last Updated:  December 30, 2014