What is ZUGFeRD / Factur-X?
ZUGFeRD ("Zentraler User Guide des Forums elektronische Rechnung Deutschland") and the technically identical French format Factur-X are hybrid e-invoices. That means a single file holds two views of the same invoice.
- A machine-readable XML following the European EN16931 standard — so the recipient's accounting software can process the invoice automatically, with no re-keying.
- A human-readable PDF — the familiar, printable invoice that any clerk can read.
The trick: both live in one file. The XML is embedded as an attachment inside a PDF/A-3. Recipients who still work manually simply open the PDF; systems that automate read the embedded XML. Nothing has to be sent twice.
Why a hybrid format?
Pure PDF invoices are convenient for people but nearly worthless to machines — every line item would have to be laboriously extracted or re-typed. Pure XML invoices (such as XRechnung) are the opposite: perfect for machines, but barely readable for people.
The hybrid format resolves this conflict: one file serves both worlds at once. The recipient decides whether to process the XML automatically or eyeball the PDF — without the sender having to manage two different documents. That is exactly why ZUGFeRD/Factur-X is regarded as the pragmatic bridge standard on the way to a purely electronic invoicing world.
One file, two readers: the PDF/A-3 is for the human eye, the embedded EN16931 CII XML for the recipient's software. Both are guaranteed to carry the same invoice content.
The upcoming mandatory B2B e-invoice
Germany is introducing the mandatory electronic invoice in the B2B sector step by step. The key points for every shop:
- Since 1 January 2025, domestic businesses must be able to receive and process structured e-invoices. A plain PDF is no longer sufficient for that.
- The obligation to send structured e-invoices is being phased in over the following years, rolling out to more businesses through 2027/2028.
ZUGFeRD/Factur-X meets this requirement because the embedded XML conforms to the European EN16931 standard — the same semantic model that XRechnung is also built on. Anyone already generating conformant hybrid invoices today is prepared for the sending obligation.
The receiving obligation is already in force. If your shop supplies B2B customers, it should be able to issue structured e-invoices — receiving has been mandatory since early 2025, and sending follows in stages. Switching early saves a scramble right before each respective deadline.
The technical stack
A conformant ZUGFeRD/Factur-X file is made of three precisely defined building blocks. Sequent generates all three and then verifies the result against them.
| EN16931 | The European semantic standard for the e-invoice. It defines which fields an invoice must contain (e.g. amounts, tax rates, payment terms) and how they are to be interpreted. |
|---|---|
| CII (Cross Industry Invoice) | The XML syntax in which the EN16931 model is expressed. This is the structured, machine-readable layer of the invoice. |
| PDF/A-3 | The archive-grade PDF format that permits arbitrary attachments. Here the CII XML is stored as an integrated attachment inside the visible PDF. |
| Result | A hybrid file: a PDF/A-3 with an embedded EN16931 CII XML — both human- and machine-readable at once. |
How Sequent implements it
Sequent generates the conformant hybrid invoice entirely inside WordPress and WooCommerce. No external service is needed, there are no per-document fees, and your invoice data never leaves your server.
- Step 1 — Generate the CII XML. From the order data in WooCommerce, Sequent builds an EN16931-conformant CII XML with all mandatory fields.
- Step 2 — Embed in PDF/A-3. The XML is embedded into the visible PDF/A-3 of the invoice — two views become one conformant hybrid file.
- Step 3 — Read back & verify. Sequent reads the embedded XML out again and verifies that the hybrid file "round-trips" cleanly — a direct proof of conformance that the XML and the PDF match.
ZUGFeRD is a Pro feature of Sequent
Conformant hybrid invoices — EN16931 CII XML inside a PDF/A-3, generated and read back directly in WordPress, with no cloud and no per-document fees.
Unlock Pro →What Sequent actually delivers
- EN16931-conformant CII XML from every WooCommerce order — including amounts, tax rates and payment terms.
- Embedding in PDF/A-3, so that a single file is both human- and machine-readable.
- Round-trip check: the embedded XML is read back and verified against the expected content.
- Everything locally in your WordPress installation — no external cloud, no per-document API fees, no data sharing.
Frequently asked questions
What is ZUGFeRD / Factur-X?
ZUGFeRD (and the technically identical French format Factur-X) is a hybrid e-invoice: a PDF/A-3 file with a machine-readable, EN16931-conformant CII XML embedded inside it. A single file is therefore both human- and machine-readable.
Do I need an external cloud service for ZUGFeRD?
No. Sequent generates the conformant hybrid invoice entirely inside your WordPress / WooCommerce installation. There is no external service and no per-document fee; your data never leaves your server.
From when must my shop be able to process e-invoices?
Since 1 January 2025, businesses in Germany must be able to receive structured B2B e-invoices. The obligation to send them is being phased in through 2027/2028.
How does ZUGFeRD differ from XRechnung?
Both are based on the EN16931 semantic standard. XRechnung is a pure XML format, whereas ZUGFeRD/Factur-X is a hybrid format: the same EN16931 CII XML, additionally embedded in a visible PDF/A-3. That makes the invoice usable by machines and people alike.