Validating e-invoices: CaRD ZUGFeRD Validator
Most companies learn whether an e-invoice is sound from the recipient — weeks later, when the payment fails to arrive. That is avoidable, and without sending a single invoice out onto the internet.
Two checks that are easily confused
A ZUGFeRD invoice consists of two parts, and either can be broken independently of the other. One is the container: a PDF in the long-term format PDF/A-3 with a correctly embedded attachment. The other is the invoice itself — the structured data, which has to satisfy the business rules of the European standard EN 16931 and, in Germany, the additional XRechnung requirements. A document can be perfectly correct in substance and still fail on the container, and the other way round.
That is why a single look is not enough: tools for invoice data never inspect the PDF container, and PDF/A checkers do not understand invoices. The CaRD ZUGFeRD Validator runs both in one pass and produces a result you can put in front of somebody — with the actual rule violations in plain language, not a red dot.
The second point is where the check happens. Invoices contain trade secrets, commercial terms and personal data. Uploading them to an online service just to find out whether a mandatory field is missing is not an option for many companies — and it does not have to be: the validator runs on your own machine or your own server. There is no upload, no sign-in and no account.
It is usable from wherever invoices actually arrive and are produced: as a check on the attachments of an open e-mail, via “Send to” in Windows Explorer, by drag and drop — or automated in batch behind an invoice run. The result is a report in the browser with one card per file checked.
At a glance
- PDF/A container and invoice XML in a single pass
- EN 16931 business rules and the German XRechnung requirements
- Runs locally — no upload, no account, no online service
- From Outlook, from Explorer, by drag and drop or in batch
- Report in the browser: one card per file, violations in plain language
- Machine-readable result for hooking into an output run
Why this matters
What happens without validation — and when it surfaces.
- The recipient rejects the invoice, the payment term keeps running
- Complaints arrive weeks later and then concern many documents
- A format error in the output run multiplies with every invoice printed
- On the inbound side it otherwise stays unclear whether the supplier or we caused it
- Online services solve the problem — and leave your invoices with a third party
What is checked
Both layers, in one run.
- PDF/A conformance of the container against the established open rule set
- Correctly embedded invoice file inside the PDF
- Invoice data against the business rules of EN 16931
- German XRechnung rules (KoSIT Schematron)
- Pure XML invoices without a PDF as well
Three routes into daily work
Validate where the invoice already is.
- From Outlook: check the attachments of the open message directly
- In Windows Explorer via “Send to”
- Drag and drop, or a call from the command line
- Whole directories in batch
- Return value for automation: valid, objected to, or aborted
The report
A result somebody can actually work with.
- HTML report in the browser, one card per file checked
- Violations in plain language instead of error numbers
- Container check and invoice check reported separately
- Forwardable to a supplier, a customer or your own department
- Old reports are cleaned up after a configurable period
Operations
Deliberately undemanding.
- One folder, all paths relative — moving it means copying it
- The required runtime environment is included
- Settings in a plain text file
- No database, no service, no cloud
- We take care of setup and of wiring it into Outlook and Explorer
Where it sits in the process
Two points of use, two different questions.
- Outbound before dispatch: is what we send out correct?
- Inbound in disputed cases: is it the supplier or is it us?
- At go-live: check every document type once
- In operation: automated samples per invoice run
- Fits with Creating e-invoices and Incoming invoices
Frequently asked questions
Are our invoices uploaded anywhere?
No. Validation runs entirely on your own machine or server. There is no upload, no sign-in and no user account. That is the main reason the tool exists: the public validators on the internet are technically sound, but they require an invoice containing commercial terms and personal data to leave the building.
What exactly is checked?
Two layers in one pass. First the PDF/A container: is the PDF really PDF/A, and is the invoice file correctly embedded? Second the invoice itself against the business rules of the European standard EN 16931 and the additional German XRechnung rules. Pure XML invoices without a PDF are checked as well.
Is a PDF/A checker not enough?
No — it only sees the container. An invoice can be a flawless PDF/A-3 and still be missing mandatory details the standard requires. Conversely the invoice can be substantively correct while the PDF misses conformance, for instance because of a font that was not embedded. Both failure modes lead to rejection at the recipient.
Can validation be automated?
Yes. The validator works on entire directories and can be called from the command line; the result comes back as a machine-readable return value — valid, objected to, or aborted. That lets you hook it in behind an invoice run so that problems surface before the documents leave the building.
Does it also work for incoming invoices?
Yes, and that is often where it is most useful. When a supplier invoice gets stuck in processing, the check answers the decisive question: is it our processing or is the invoice itself faulty? With the report in hand that can be settled with the supplier instead of guessed at.
How do we get the validator?
Through us. We provide it, set it up and wire it into Outlook and Windows Explorer so it is reachable from the workplace without detours. Talk to us — in that conversation we also work out at which points in your process validation actually pays off.
Does this match your project?
Talk directly to our consultants — no detours.