E-Invoice Conformance Lab
DE

XRechnung · ZUGFeRD / Factur-X · Peppol UBL

Find out why your e-invoices fail validation — and how to fix them.

We run your invoices, or your software's output, through the official KoSIT validator, the EN 16931 schematron and Peppol BIS 3 rules. You get a plain report: what fails, where, and what to change.

Free check: send one invoiceSee pricing

What you get

Multi-validator run

KoSIT XRechnung configuration, CEN EN 16931 schematron (UBL and CII), XSD schema and Peppol BIS 3 — the same tooling as our public matrix.

Clear findings

Every rule failure per invoice: rule ID, location in the file, message — plus cases where one validator accepts and another rejects.

Fix guidance

For each finding: which field or calculation is wrong and what your generator should write instead. Optional re-check after your fix.

Pricing

Fixed prices. We confirm scope in writing before you pay.

Free check

0 €
One invoice

Findings summary within 2 business days. No account, no payment.

Send invoice
Most requested

One-time check

290 €
Up to 10 invoices

Full report with rule IDs and fix guidance per invoice, within 3 business days.

Order — pay by bank transferRequest by email

Library / vendor audit

790 €
Your generator's output

Systematic test cases across VAT categories S, E, AE, K, G, O, allowances/charges and rounding. Includes one re-test after your fix.

Order — pay by bank transferRequest by email

Monitoring

99 € / month
Ongoing

Re-run your test set after each release of your generator and after validator rule updates; notification when something breaks.

Request by email

How to pay

PayPal

After we confirm the scope by email, pay with the PayPal button on the package. Card payments via PayPal are possible without a PayPal account where PayPal supports it.

Bank transfer (SEPA)

Click “Order — pay by bank transfer”. We confirm the scope and send you an invoice that contains the bank details. Bank details are never published on this site.

Unsure which package fits? Start with the free check — no payment needed.

Free check: send one invoice

Findings summary within 2 business days. No account, no payment.

Send invoice

conformance@mail.grokbot.com

Proof: public, verifiable work

We maintain an open conformance matrix that tests e-invoice libraries against the official validators. Issues found with this tooling were reported publicly to open-source maintainers — you can check every link.

Open the conformance matrix

Status as of 20 Oct 2026:

ProjectReportStatus
speedata/einvoice#185Fixed via PR #186; released in v0.0.23 (re-tested: 9/9 UBL repro invoices KoSIT-acceptable)
ZUGFeRD/mustangproject#1316Fixed on master (PR #1318), unreleased
horstoeko/zugferd#390Released in v1.0.133 (re-tested: E/AE/K/G/O exemption reasons KoSIT-acceptable)
WooCommerce PDF Invoices (WP Overnight)#1662Open
josemmo/einvoicing#93Open
ZUGFeRD-csharpDiscussion #986Known issue, workaround: set only one of PersonName/DepartmentName (see discussion #986)

How it works

  1. Email us your formats, profiles and generator version (or use the free check).
  2. We confirm scope and price in writing.
  3. You send test invoices — synthetic or anonymised, please no real personal data.
  4. You receive the report. Pay by PayPal or bank transfer.

FAQ

Which formats do you check?

XRechnung (UBL and CII), ZUGFeRD / Factur-X (PDF with embedded XML, EN 16931 profiles) and Peppol BIS Billing 3.0 UBL.

Do you fix my software?

We tell you exactly what to change and re-check after your fix (audit package). Changes to your code are made by you or your developer.

Is this legal or tax advice?

No. A passing check means the listed validators accepted the documents at the time of testing.

What happens to my files?

They are used only for your check and deleted after 30 days. Please send test or anonymised data.

Are you affiliated with KoSIT?

No. This is an independent project using the publicly available official validation artefacts.