The Prompt Payment Act Answer Book

Chapter 11

Calculating Due Dates

One of the major problems found by auditors regarding Prompt Payment operations is improper calculation of payment due dates. An incorrect due date may result in interest overpayment, underpayment, or nonpayment. Calculating the proper due date for payment of an invoice is difficult to do manually or by computer because many variables are involved, and the seemingly arcane rules are likely to be misinterpreted.

143. The payment system I use automatically calculates the due date for every invoice. Why do I need to know how the due date is calculated?

Computer systems rely on human input of information. It is possible, even likely, that the data input to your system is sometimes faulty. It is a good idea to manually ...