The digitalization of business processes is a crucial method for cutting down administrative costs, improve productivity in business processes, and achieving process transparency. Since invoices are some of the most important documents exchanged between business partners, it makes sense that in-voices be sent and received electronically. There are no formal rules that determine the format of elec-tronic invoices. However, companies benefit most when invoices contain structured data that can be processed automatically. The acceptance and adoption of structured electronic invoicing is generally rather low in the European Union, but it differs significantly among European countries. The elec-tronic data interchange with the invoice standard EDIFACT is most favored by larger companies. An XML-based invoice could fill the gap between EDIFACT invoices and unstructured invoices like PDF and paper invoices. Some European countries have already established a national XML-based invoice standard. This paper addresses critical success factors to the adoption of XML-based standards. In an explorative study with experts, various aspects of acceptance were derived, and the results adapted to the Technology-Organization-Environment framework.