Described herein are methods and apparatus for the processing of electronic invoices. A server for processing invoices communicates with computing systems such as a supplier system (used by a supplier), a buyer system (used by a buyer), and finance systems (which manage bank accounts of the supplier and buyer). The server communicates with the supplier system and the buyer system regarding an electronic invoice that relates to a transaction between the supplier and the buyer, and that includes a unique identification code. When the buyer has approved the electronic invoice, the supplier system and/or the server is able to settle the invoice using the unique identification code.