Abstract This Invoicing System process is an important part of a wider set of business processes including the placing and acceptance of an order, delivery and payment methods. Electronic Invoicing enables sending, receiving and processing invoices without manual intervention. It allows enterprises to benefit from shorter payment delays, fewer errors, as well as reduced printing and postage costs. However, introducing the exchange of electronic invoices is often complex and costly, in particular for small and medium-sized enterprises. Besides that, there is a large number of XML-based standards aimed at representing an electronic invoice, which makes an obstacle for wider adoption and implementation of electronic invoicing. In this paper, we present our electronic invoicing system which enables enterprises, especially the small and medium-sized ones, with a low cost simple and safe access to the world of electronic business. The developed web application enables issuing, receiving, and viewing electronic invoices, storage of invoice data, and connection to the registry of electronic invoice recipients and senders. Particular attention is given to the conversion between XML-based electronic invoice standards UBL 2.0 and OAGIS 8.0, as well as to the security of the system.