Syllabus

Electronic Data Interchange, EDI, combines the meaning of a format with the addressing and exchange of a protocol. Despite being more complex, EDI is much older than XML based e-invoicing, and still in use today. The introduction of (international) e-invoicing standards in germany in fact dates back to the 1977 introduction of EDIFACT.

The XML Application error and acknowledgement messages can be used to signal acceptance or rejection of invoices

Unstructured invoices are human-readable (e.g. image files, TIFF, PDF even with OCR layer), structured invoices are machine readable (e.g. XML files). Unstructured invoices are generally easier to obtain, e.g. by scanning paper invoices, but they can not be processed automatically.

but later replaced by it’s own standard. There are slight differences between OASIS UBL and UN/CEFACT, their extentability, their governance, and their institutions.

In 2014 ZUGFeRD defined how to embed XML in PDF to get a hybrid invoice, both structured and unstructured at the same time. PDF/A was selected as the carrier, a customized UN/CEFACT CII/2013b for the data and three subsets („profiles“) were defined.

ZUGFeRD version 2~=Factur-X version 1 switched UN/CEFACT CII from a customized 2013b to a unchanged 2016b version, introduced first two more profiles and renamed one. Later, in v2.1.1, the concept of reference profiles were conceived.

Factur-X 1 started as a french fork of ZUGFeRD 2 led by the FNFE. The „Factur-X namespace“ soon also became the recommended name(space?) for ZUGFeRD.

Order-X is the sister standard to Factur-X, with in PDF embedded XML of orders instead of invoices. Process-wise it also supports proposal and acceptance of changes. For this purpose, UN/CEFACT CrossIndustryOrder 2020b is used, the embedded file is called Order-X.xml.

GS1 and BVL were working on hybrid electronic despatch advices based on UN/CEFACT Cross Industry Despatch Advice, crossing the gap between orders and invoices, which will be the basis for the upcoming Deliver-X standard

The different lists of the different standards for eligible attribute values have been centralized by the CEF, who republish them as excel. They are binding for EN16931, i.e. not only CII but also UBL.

The XRechnung is the requirements specification of the german government vis a vis electronic invoices. XML-wise they are mapped to CII and UBL and it makes certain attributes mandatory, e.g. the postal address of the receiver and a seller contact as well as the governmental routing number „Leitweg-ID“. Due to political reasons cash discounts are handled using a proprietary format, not XML. This lesson clarifies Business Term IDs, how to find them (and their cardinalities) in ZUGFeRD’s technical appendix, which industry recommendation exists, what the difference is between the two XRechnung profiles, how to convert between the XML formats, how to validate XRechnung, how to visualize them and how they are mapped to Peppol-IDs to facilitate automatic transmission.

Invoice attachments like protocols, bills of material or measurements are added either as embedded file within the PDF (Factur.-X) or base64-encoded in the XRechnung.

Specifications, CIUS, like the german XRechnung, can make optional attributes mandatory, Andreas Starke’s additional data can cater additional structured attributes for electronic invoices.

E.g. the Deutsche Bahn or the construction industry has published requirements vis á vis Xrechnung respective ZUGFeRD files, and the french Chorus Pro has published requirements both for french B2G as well as for french B2B invoices.

PEPPOL is a international EDI organization, based on UBL messages and the AS/4 protocol, which implement a four-corner model for their paying customers.

E-Billing, in Germany for amounts <150 Eur, allow amounts with VAT which could otherwise not be expressed, e.g. 20,20 Eur @ 19%.

Apart from usual invoices, sometimes there might be need for reminders (not in scope), credit notes, or corrected invoices. Partial invoice are in scope, collective invoices (single invoice on multiple orders) only available in certain profiles.

Open Source SDKs for C++, Java, Python and PHP are covered

Open source tools for Metadata and schema validation

Which free libraries can be used to make software e.g. Factur-X ready

Free software and editors which perform e.g. schema validation for XML authoring

Free open source private banking software and e-invoice viewers

Free software to re-calculate invoices and check their formal correctness

XRechnung and Factur-X/ZUGFeRD consist of XML files, this convers XML’s validity, in general, tools to validate, address, mix and transform XML and gives an intro to the two most important XML formats for electronic invoices, UN/CEFACT Cross Industry Invoice (used for Factur-X/ZUGFeRD and XRechnung) and UBL (used for XRechnung and Peppol)

UN/CEFACT CII is a standard used for electronic invoices, the „MUG“ has been determined as it’s european subset. For orders, CIO can be used. The current version, schema file, the root, the basic elements and the basic namespaces are described.

UBL is another XML invoice standard. Alternative XML structures and why they are deprecated are discussed (e.g. OpenTrans, FinInvoice). Here as well the current version, schema file, the root, the basic elements and the basic namespaces are described.

XSL transformations allow to transform any XML file in one format into anotther file in the same, or a different format.

much more powerful validation than mere Schema files can do, allowing e.g. mathematical operations like the total amount has to match the sum of the items. Which e-invoice related schematron files are published where is part of this lesson.

Codelists specify possible attribute values, e.g. „H87“ as unit code for „piece“. Which e-invoice related codelists are published where and which versions are relevant is part of this lesson. 1.

Like XML, PDF is a hierarchical format, but with references, binary data and compression

Ghostscript is one of the very few free open source tools capable of converting PDF to PDF/A. It is often used in virtual PDF printing software and actually Ghostscript can read and process PDF files so well that it is occasionally used to fix even corrupted PDFs. Even Factur-X comliant PDF/A-3 can be created with Ghostscript.

Open-Source tools like itext RUPS, Exiftool, or the structure view of the commercial Acrobat Pro highlight the internal hierachy or metadata within the PDF files.

This lesson will discuss the difference between PDF and it’s archival counterparts, PDF/A-1 to 4 and why it is important to at least use PDF/A-1

The knowledge of the aforementioned tools, along with the specifications (PDF is available, PDF/A costs money) can help to make files valid and more readable

Within PDF/A, file attachments are available since A-3, this lesson also has a look at the A-3 subset a, u and b, as well as PDF/A-4‘s „f“ subsubset.

How to use the command line tool to extract XML from Factur-X/ZUGFeRD

Use the command line tool to combine XML and PDF to Factur-X/ZUGFeRD and Order-X

Validation with the command line tool, meaning of the error types. How to follow up on rounding errors.

How the commandline can be used to convert ZUGFeRD from v1 to v2, from CII to UBL and (for the purpose of visualization) from CII to HTML. How Mustang can be used in automated tests.