Abstract: An electronic bill presentment and payment system for presenting an invoice of a vendor to a customer comprises a billing database for storing an invoice file. The invoice file comprises a line value representing an amount payable by the customer for a product provided by the vendor, a tax value representing an amount payable as a tax on the product, and a fee value representing an amount payable as a fee on the product. An application server provides for receiving a request to adjust the line value from the customer, providing instructions to replace the line value with an adjusted line value, calculating an adjusted tax value and an adjusted fee value based on the adjusted line value, and providing instructions to replace the tax value with the adjusted tax value. Where appropriate, flat fee adjustments are also made.

Abstract: An electronic bill presentment and payment system for presenting an invoice of a vendor to a customer comprises a billing database for storing an invoice file. The invoice file comprises a line value representing an amount payable by the customer for a product provided by the vendor, a tax value representing an amount payable as a tax on the product, and a fee value representing an amount payable as a fee on the product. An application server provides for receiving a request to adjust the line value from the customer, providing instructions to replace the line value with an adjusted line value, calculating an adjusted tax value and an adjusted fee value based on the adjusted line value, and providing instructions to replace the tax value with the adjusted tax value.