The invoicing party has to provide two files in preparation of the digital signing of a bill. The one has to contain the bill generated by a word processing, the enterprise resource planning system (e.g. PDF or Word document) and the other one has to contain the bill’s core data having to be signed (compulsory billing data like names and address of the document author and document receiver, description of the service, invoice values, applicable purchase tax rate, purchase tax and so on). The signing service has to be able to distinguish the two files on the base of the provided file names. With the complete transmission of the document data the document is automatically signed and is provided for the invoicing party in signed form. Almost all common entry formats are supported and read by the signing service. The issue of the signed documents takes place basically in the format of the entry document. The bill’s core data have to be applied in the CVS format which is supported by many software programs for office applications, enterprise resource planning or ERP system standard.