ZUGFeRD API for generated invoices
Generators check the XSD. The EN 16931 business rules — totals, VAT breakdown, mandatory fields — need schematron. This API runs them in one call.
curl -H "Authorization: Bearer $FINEKOT_KEY" -F file=@invoice.xml https://api.finekot.com/v1/e-invoice
{
"valid": false,
"verdict": "technically_invalid",
"profile": {"name": "XRechnung 3.0"},
"errors": 3, "warnings": 1,
"issues": [
{"rule": "BR-DE-15", "severity": "error",
"message": "Das Element \"Buyer reference\" (BT-10) muss übermittelt werden.",
"location": "/ubl:Invoice[1]"},
…
],
"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 drafthorse output before it leaves your system
drafthorse validates the XSD in serialize(); a file can pass it and still break BR-CO-14 or BR-S-08. The API returns those violations with XPath.
import os, requests
from drafthorse.models.document import Document
doc = Document()
# … fill doc.context, doc.header and doc.trade as in the drafthorse README
xml = doc.serialize(schema="FACTUR-X_EN16931") # drafthorse checks the XSD here
r = requests.post("https://api.finekot.com/v1/e-invoice",
headers={"Authorization": f"Bearer {os.environ['FINEKOT_KEY']}"},
files={"file": ("factur-x.xml", xml, "application/xml")},
timeout=60)
rep = r.json()
if not rep["valid"]: # business rules BR-*, BR-CO-*, BR-S-*: not covered by the XSD
raise SystemExit([(i["rule"], i["message"]) for i in rep["issues"]
if i["severity"] == "error"])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.
XSD is not enough
The Factur-X XSD checks structure: element names, order, data types. EN 16931 adds about 200 business rules on top: sums must add up (BR-CO-10 to BR-CO-17), each VAT category needs its breakdown (BR-S-*, BR-AE-*), mandatory fields must be filled.
The API reads the profile from the guideline id and applies EN 16931 1.3.17, plus KoSIT XRechnung rules for the XRECHNUNG profile. MINIMUM and BASIC WL are reported as not EN 16931 invoices.
To build the PDF instead of only checking it, send invoice JSON with op=create and output=pdf: €0.04 per document.
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