ZUGFeRD validator API for PDF/A-3 invoices
Post the hybrid PDF as it is. The API finds factur-x.xml inside, reads the profile and checks the XML against the EN 16931 rules.
curl -H "Authorization: Bearer $FINEKOT_KEY" -F file=@invoice.pdf https://api.finekot.com/v1/e-invoice
{
"valid": true,
"verdict": "technically_valid",
"container": "pdf",
"attachment": "factur-x.xml",
"profile": {"name": "Factur-X / ZUGFeRD EN 16931 (COMFORT)"},
"errors": 0, "warnings": 0,
"issues": [],
"cost": 0.02, "balance": 0.98
}No subscription, no contract.
create from JSON €0.04 · PDF → XRechnung €0.10
A subscription bills the same monthly plan for 10 invoices or 1,000. Here you prepay any amount and pay per call; unused credit stays.
10 free checks a day · €1 free with a key · then €0.02 per check
Check node-zugferd output in Node.js
Use the EN16931 or BASIC profile in node-zugferd: MINIMUM and BASIC WL are not EN 16931 invoices and do not meet the German requirement.
// pdfA: the PDF/A-3 returned by node-zugferd
// const pdfA = await invoice.embedInPdf(pdf, { … })
const form = new FormData();
form.append("file", new Blob([pdfA], { type: "application/pdf" }), "invoice.pdf");
const res = await fetch("https://api.finekot.com/v1/e-invoice", {
method: "POST",
headers: { Authorization: `Bearer ${process.env.FINEKOT_KEY}` },
body: form,
});
const rep = await res.json();
console.log(rep.attachment, rep.profile.name, rep.verdict);
// factur-x.xml Factur-X / ZUGFeRD EN 16931 (COMFORT) technically_valid
for (const i of rep.issues) console.log(i.severity, i.rule, i.location);
if (!rep.valid) process.exitCode = 1;Validate an e-invoice
Official EN 16931 and XRechnung rules. Errors with rule id, message and location.
10 free checks a day · €1 free with a key · then €0.02 per check
Processed on servers in Germany (Hetzner, Falkenstein). The uploaded file is checked in memory and not stored.
The verdict, profile, totals and every rule violation appear here.
How the PDF is checked
The attachment is found by name (factur-x.xml, zugferd-invoice.xml, xrechnung.xml) and returned in the attachment field. Since 2025 the XML is the leading part of a ZUGFeRD invoice in Germany (BMF FAQ, question 12a).
The XML is checked with EN 16931 1.3.17; the XRECHNUNG profile also gets KoSIT XRechnung schematron 2.6.0. PDF/A-3 conformance of the container is not checked: use veraPDF for that.
A plain PDF without an attachment returns 422 pdf_no_xml_attachment and is not charged.
Price in plain numbers
A prepaid balance, no subscription. Charged only for a successful answer; errors are free.
A new key comes with €1 of free credit: 50 validations.
Credits never expire. No subscription.
Apple Pay, Google Pay or card on the monobank page. The key is created for you if you have none.
No key in this browser yet.
For developers
Same checks over REST and MCP. One header, JSON out.
curl https://api.finekot.com/v1/e-invoice \
-H "Authorization: Bearer fk_live_…" \
-F file=@invoice.xml
# → {"valid":false,"errors":2,"issues":[{"rule":"BR-DE-15",…}]}
# X-Cost: 0.02curl https://api.finekot.com/v1/e-invoice \
-H "Authorization: Bearer fk_live_…" \
-H "Content-Type: application/json" \
-d '{"op":"create","output":"pdf","invoice":{…}}'
# → Factur-X PDF url + validation report · X-Cost: 0.04claude mcp add --transport http finekot https://api.finekot.com/mcp --header "Authorization: Bearer fk_live_…"
Full reference: /llms.txt · /openapi.json · /.well-known/mcp.json