ISDOC is an electronic invoicing format that enables paperless exchange of invoices and other documents, fast processing and portability between businesses, public administrations, and private individuals, defined by the "Working Group on Electronic Data Interchange Standards" of the ICT Union (formerly SPIS). Currently, the Ministry of the Interior is the holder of the ISDOC format licence and trademark.
The ISDOC format is now an integral part of the vast majority of economic and ERP systems sold on the Czech market, such as ABRA Gen ERP and ABRA Flexi.
https://isdoc.org/
Preferably in Czech language.