we can generate Peppol Bis 3.0 conform xml invoices when our partners have an (Luxembourgish) VAT ID. In the XML the VAT is used to create the EndpointID and the CompanyID. A lot of administrations use a separate Peppol ID, that lacks an 'LU'-prefix. We don't know how to get this extra Peppol ID into the XML invoice, the customers view does offer such a field ad default. We added an extra field Peppol ID in the res.partner model, but we don't know how to get this field to be used in the generated XML invoice who needs both fields (EndpointID = Peppol ID and the CompanyID = VAT ID).