Part of the ZUGFeRD community: https://github.com/zugferd

Implementing and maintaining this library is a lot of hard work. I'm doing this in my spare time, there is no company behind developing ZUGFeRD-csharp. Support me in this work and help making this library better:

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In particular, I am searching for sponsors for:

• Complete UBL format support (reading and writing)
• Validation using the standard XSL
• Invoice visualization

The ZUGFeRD library allows to create XML files as required by German electronic invoice initiative ZUGFeRD as well invoices in the successor Factur-X. One special profile of Factur-X is the German XRechnung format. The library is meant to be as simple as possible, however it is not straight forward to use as the resulting XML file contains a complete invoice in XML format. Please take a look at the ZUGFeRD-Test project to find sample creation code. This code creates the same XML file as shipped with the ZUGFeRD information package.

Since there are a lot of terms and standards around electronic invoices, I'd like to lay out my understanding:

• ZUGFeRD was developed by a German initiative as a standard for electronic invoices (https://www.ferd-net.de/).
• ZUGFeRD 2.1 is identical to the German/French cooperation Factur-X (ZUGFeRD 2.1 = Factur-X 1.0) (https://www.ferd-net.de/standards/what-is-factur-x/index.html).
• The standard Factur-X 1.0 (respectively ZUGFeRD 2.1) is conform with the European norm EN 16931.
• EN 16931 in turn is based on worldwide UN/CEFACT standard 'Cross Industry Invoice' (CII).
• XRechnung as another German standard is a subset of EN 16931. It is defined by another party called KoSIT (https://www.xoev.de/). It comes with its own validation rules (https://www.ferd-net.de/standards/what-is-xrechnung/index.html).
• This means that both Factur-X 1.0 (respectively ZUGFeRD 2.1) and XRechnung are conform with EN 16931. This does not automatically result that those invoices are per se identical
• To achieve compatibility, ZUGFeRD 2.1.1 introduced a XRechnung reference profile to guarantee compatibility between the two sister formats

Subject to the Apache license http://www.apache.org/licenses/LICENSE-2.0.html

Just use nuget or Visual Studio Package Manager and download 'ZUGFeRD-csharp'.

You can find more information about the nuget package here:

https://www.nuget.org/packages/ZUGFeRD-csharp/

Prerequisites:

• Visual Studio >= 2017
• .net Framework >= 4.6.1 (for .net Standard 2.0 support)

Open ZUGFeRD/ZUGFeRD.sln solution file. Choose Release or Debug mode and hit 'Build'. That's it.

For running the tests, open ZUGFeRD-Test/ZUGFeRD-Test.sln and run the unit tests. The tests show good cases on how to use the library.

Central class for users is class InvoiceDescriptor. This class does not only allow to read and set all ZUGFeRD attributes and structures but also allows to load and save ZUGFeRD files.

However, the standard has become quite large during the recent years. So it is worthwhile to go through the creation process step by step.

InvoiceDescriptor desc = InvoiceDescriptor.CreateInvoice("471102", new DateTime(2013, 6, 5), CurrencyCodes.EUR, "GE2020211-471102");
desc.Name = "WARENRECHNUNG";
desc.ReferenceOrderNo = "AB-312";
desc.AddNote("Rechnung gemäß Bestellung Nr. 2013-471331 vom 01.03.2013.");
desc.AddNote("Es bestehen Rabatt- und Bonusvereinbarungen.", SubjectCodes.AAK);
desc.SetBuyer("Kunden Mitte AG", "69876", "Frankfurt", "Kundenstraße 15", CountryCodes.DE, "88", new GlobalID(GlobalIDSchemeIdentifiers.GLN, "4000001123452"));
desc.AddBuyerTaxRegistration("DE234567890", TaxRegistrationSchemeID.VA);
desc.SetBuyerContact("Hans Muster");
desc.SetSeller("Lieferant GmbH", "80333", "München", "Lieferantenstraße 20", CountryCodes.DE, "88", new GlobalID(GlobalIDSchemeIdentifiers.GLN, "4000001123452"));
desc.AddSellerTaxRegistration("201/113/40209", TaxRegistrationSchemeID.FC);
desc.AddSellerTaxRegistration("DE123456789", TaxRegistrationSchemeID.VA);
desc.SetBuyerOrderReferenceDocument("2013-471331", new DateTime(2013, 03, 01));
desc.SetDeliveryNoteReferenceDocument("2013-51111", new DateTime(2013, 6, 3));
desc.ActualDeliveryDate = new DateTime(2013, 6, 3);
desc.SetTotals(202.76m, 5.80m, 14.73m, 193.83m, 21.31m, 215.14m, 50.0m, 165.14m);
desc.AddApplicableTradeTax(129.37m, 7m, TaxTypes.VAT, TaxCategoryCodes.S);
desc.AddApplicableTradeTax(64.46m, 19m, TaxTypes.VAT, TaxCategoryCodes.S);
desc.AddLogisticsServiceCharge(5.80m, "Versandkosten", TaxTypes.VAT, TaxCategoryCodes.S, 7m);
desc.AddTradePaymentTerms("Zahlbar innerhalb 30 Tagen netto bis 04.04.2018", new DateTime(2018, 4, 4));
desc.AddTradePaymentTerms("3% Skonto innerhalb 10 Tagen bis 15.03.2018", new DateTime(2018, 3, 15), PaymentTermsType.Skonto, 30, 3m);

Optionally, to support Peppol, an electronic address can be passed:

desc.SetSellerElectronicAddress("DE123456789", ElectronicAddressSchemeIdentifiers.GermanyVatNumber);
desc.SetBuyerElectronicAddress("LU987654321", ElectronicAddressSchemeIdentifiers.LuxemburgVatNumber);

The fields are only necessary if you want to send the XRechnung via the Peppol network. A description of the fields can be found in the following documents:

https://docs.peppol.eu/edelivery/policies/PEPPOL-EDN-Policy-for-use-of-identifiers-4.1.0-2020-03-11.pdf

https://www.ferd-net.de/upload/Dokumente/FACTUR-X_ZUGFeRD_2p0_Teil1_Profil_EN16931_1p03.pdf

In Luxembourg, it has been mandatory since this year to process all invoices via Peppol:

https://gouvernement.lu/de/dossiers.gouv_digitalisation%2Bde%2Bdossiers%2B2021%2Bfacturation-electronique.html

In Germany, this has so far only been necessary for invoices in the course of a public contract from the federal government:

https://www.e-rechnung-bund.de/ubertragungskanale/peppol/

The library allows to operate in two modes: you can either let the library generate the line ids automatically or you can alternatively pass distinct line ids. This is helpful if you want to convert existing invoices, e.g. from ERP systems, to ZUGFeRD/ Factur-X.

To let the library create line ids, you can use:

InvoiceDescriptor desc = InvoiceDescriptor.CreateInvoice("471102", new DateTime(2013, 6, 5), CurrencyCodes.EUR, "GE2020211-471102");
desc.AddTradeLineItem("Item name", "Detail description", QuantityCodes.C62, ....);

This will generate an invoice with trade line item numbered as '1'.

To pass pre-defined line ids, this is the way to go:

InvoiceDescriptor desc = InvoiceDescriptor.CreateInvoice("471102", new DateTime(2013, 6, 5), CurrencyCodes.EUR, "GE2020211-471102");
desc.AddTradeLineItem(lineID: "0001", "Item name", "Detail description", QuantityCodes.C62, ....);
desc.AddTradeLineItem(lineID: "0002", "Item name", "Detail description", QuantityCodes.C62, ....);

which will generate an invoice with two trade line items, with the first one as number '0001' and the second one as number '0002'.

Product characteristics are used to add information for the specified trade product in the 'ApplicableProductCharacteristic' section. One trade product can have one or more product characteristics, which can contain description, value, typecode and value measurand elements.

// you can optionally add product characteristics:
desc.TradeLineItems.Add(new TradeLineItem("0003")
{
   ApplicableProductCharacteristics = new List<ApplicableProductCharacteristic>
   {
       new ApplicableProductCharacteristic()
       {
           Description = "Description",
           Value = "Value"
       }
   }
});

The library allows to add special references to an invoice which are pretty rare but nevertheless supported:

// you can optionally add a reference to a procuring project:
desc.SpecifiedProcuringProject = new SpecifiedProcuringProject {Name = "Projekt AB-312", ID = "AB-312"};

// you can optionally reference a contract:
desc.ContractReferencedDocument = new ContractReferencedDocument {ID = "AB-312-1", IssueDateTime = new DateTime(2013,1,1)};

The library supports setting a status code and a reason for each line item. This feature helps clarifying whether a line item contributes to the invoice total or is for information only. It can be useful for marking items as informational, subtotal lines, or fully processed items, adding context to each invoiced item.

// Example: Adding a trade line item with a specific status and reason
TradeLineItem tradeLineItem3 = desc.AddTradeLineItem(
    name: "Abschlagsrechnung vom 01.01.2024",
    billedQuantity: -1m,
    unitCode: QuantityCodes.C62,
    netUnitPrice: 500,
    categoryCode: TaxCategoryCodes.S,
    taxPercent: 19.0m,
    taxType: TaxTypes.VAT
);

// Set a line status code and reason code to indicate that this line is for documentation only
tradeLineItem3.SetLineStatus(LineStatusCodes.DocumentationClaim, LineStatusReasonCodes.INFORMATION);

FileStream stream = new FileStream(filename, FileMode.Create, FileAccess.Write);
desc.Save(stream, ZUGFeRDVersion.Version23, Profile.XRechnung);
stream.Flush();
stream.Close();    

In order to load ZUGFeRD files, you call InvoiceDescriptor.Load(), passing a file path like this:

InvoiceDescriptor descriptor = InvoiceDescriptor.Load("zugferd.xml");

alternatively, you can pass an open stream object:

Stream stream = new FileStream("zugferd.xml", FileMode.Open, FileAccess.Read);
InvoiceDescriptor descriptor = InvoiceDescriptor.Load(stream);

The library will automatically detect the ZUGFeRD version of the file and parse accordingly. It will automatically be chosen which XRechnung version to use depending on the current date. The lifecycle of the stream is not influenced by the ZUGFeRD library, i.e. the library expects an open stream and will not close if after reading from it.

For saving ZUGFeRD files, use InvoiceDescriptor.Save(). Here, you can also pass a stream object:

InvoiceDescriptor descriptor = InvoiceDescriptor.CreateInvoice(......);

// fill attributes and structures

FileStream stream = new FileStream(filename, FileMode.Create, FileAccess.Write);
descriptor.Save(stream, ZUGFeRDVersion.Version1, Profile.Basic);
stream.Flush();
stream.Close();            

As you see, the library does not influence the lifecycle of the stream, i.e. it is not automatically closed by the library. Just as opening the stream, flushing and closing is the duty of the calling function.

Alternatively, you can pass a file path:

InvoiceDescriptor descriptor = InvoiceDescriptor.CreateInvoice(......);

// fill attributes and structures

descriptor.Save("zugferd.xml", ZUGFeRDVersion.Version1, Profile.Basic);          

Optionally, you can pass the ZUGFeRD version to use. Currently, the default version is 1.x, e.g.:

InvoiceDescriptor descriptor = InvoiceDescriptor.CreateInvoice(......);

// fill attributes and structures


descriptor.Save("zugferd-v1.xml", ZUGFeRDVersion.Version1, Profile.Basic); // save as version 1.x
descriptor.Save("zugferd-v20.xml", ZUGFeRDVersion.Version20, Profile.Basic); // save as version 2.0
descriptor.Save("zugferd-v23.xml", ZUGFeRDVersion.Version23, Profile.Basic); // save as version 2.3

For reading and writing XRechnung invoices, please see below.

In general, creating XRechnung files is straight forward and just like creating any other ZUGFeRD version and profile:

descriptor.Save("xrechnung.xml", ZUGFeRDVersion.Version23, Profile.XRechnung);

This will save the invoice as XRechnung 3.0.1 as valid from 2024/02/01.

Make sure to also add a business process which is required starting with XRechnung 3.0.1:

desc.BusinessProcess = "urn:fdc:peppol.eu:2017:poacc:billing:01:1.0";

Furthermore, XRechnung comes with some special features. One of these features is the ability to embed binary files as attachments to the xrechnung.xml document:

InvoiceDescriptor desc = _createInvoice();
byte[] data = System.IO.File.ReadAllBytes("my-calculation.xlsx");
desc.AddAdditionalReferencedDocument(
    id: "calculation-sheet",
    typeCode: AdditionalReferencedDocumentTypeCode.ReferenceDocument,
    name: "Calculation as the basis for the invoice",
    attachmentBinaryObject: data,
    filename: "my-calculation.xlsx");

desc.Save("xrechnung.xml", ZUGFeRDVersion.Version23, Profile.XRechnung);            

The resulting xrechnung.xml file will then contain the calculation file content. As this is not standardized, the decision was to encode the attachments in base64. Please note that there are only few mime-types supported by the XRechnung standard. The supported mime-types are defined in BG-24 and BT-125. At the time of writing this tutorial, those are also listed in the discussion you find over here: https://projekte.kosit.org/xrechnung/xrechnung/-/issues/59

• application/pdf
• image/png
• image/jpeg
• text/csv
• application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
• application/vnd.oasis.opendocument.spreadsheet
• application/xml

For french companies, a dedicated profile exists called E-Reporting. This profile is implemented on top of XRechnung/ Factur-X. It is used when transactions are done to customers who don't make use of VAT. One example are private customers (in B2C scenarios). The other example is when selling to entities beyond France. More information can be found here: https://www.impots.gouv.fr/e-reporting-la-transmission-de-donnees-de-transaction-ladministration (French) And here: https://www.roedl.de/themen/frankreich-e-invoice-reporting-umsatzsteuer-digital (german)

Thanks to @Athilla, this profile is also supported by ZUGFeRD-csharp.

The information that is written into the invoice descriptor is identical to standard XRechnung/ Factur-X invoices, you just need to adjust the profile:

descriptor.Save("factur-x.xml", ZUGFeRDVersion.Version23, Profile.EReporting);

This information needs to be sent to the tax authorities. Different due dates apply for implementation for different sizes of companies.

The library contains support for all profiles that are supported by the ZUGFeRD formats:

Please note that version 1 implementation of the library is not strict, i.e. it will output all information available into the invoice xml, regardless of the profiles that is used. Reading various files with different profiles will generate the correct output.

If you want to write the invoice xml with a certain ZUGFeRD version and a certain profile, make sure to use the parameters of the Save method:

descriptor.Save("zugferd-v1.xml", ZUGFeRDVersion.Version1, Profile.Basic); // save as version 1.x, profile Basic
descriptor.Save("zugferd-v20.xml", ZUGFeRDVersion.Version20, Profile.Basic); // save as version 2.0, profile Basic
descriptor.Save("zugferd-v23.xml", ZUGFeRDVersion.Version23, Profile.Basic); // save as version 2.3, profile Basic
descriptor.Save("zugferd-v23-xrechnung.xml", ZUGFeRDVersion.Version23, Profile.XRechnung); // save as version 2.3, profile XRechnung

I am frequently asked how to extract the ZUGFeRD / Factur-X / XRechnung attachment from existing PDF files.

There is a nice article on Stack Overflow on how this can be achieved using itextsharp:

https://stackoverflow.com/a/6334252

and this one covers the same with itext7 which is the successor of itextsharp:

https://stackoverflow.com/a/37804285

It is also possible to add the XML ZUGFeRD or XRechnung attachment to PDF files using itextsharp. You find information about this here:

https://stackoverflow.com/questions/70597318/af-reference-to-file-embedded-into-a-pdf-with-itextsharp

• The solution is used in CKS.DMS and supported by CKSolution: https://www.cksolution.de
• ZUGFeRD 2.1 implementation was done by https://netco-solution.de and used in netCo.Butler

You can find more information about ZUGFeRD here: https://www.ferd-net.de/