A payment disallow mechanism for an e-billing system (100) including a computer system (200) accessible for on-line interactive communication of invoices to users. The computer system including a database for storing customer invoice information, the information including an invoice date and a total invoice amount for display to said customer for on-line interaction; a mechanism for initiating electronic payment of the modified total invoice amount via the e-billing system, and a mechanism for determining whether the total invoice amount is a zero balance or credit balance prior to executing the electronic payment, wherein in response to determination of the zero or credit balance, the mechanism terminating the payment mechanism and generating a disallow payment message for display to the customer.