Business Interoperability Specifications (BIS) for common eProcurement processes. The eProcurement specifications (PEPPOL BIS) maintained by OpenPEPPOL. The PEPPOL BIS are formal requirements to ensure pan-European interoperability of procurement documents, such as eInvoices. https://peppol.eu/what-is-peppol/peppol-profiles-specifications/ Bis 3 comply to the european norm