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Introduction
What Summand is, which e-invoices it checks, how close it is to the official validator, and what it does not do.
Summand checks incoming e-invoices in TypeScript. It reads XRechnung, ZUGFeRD and Factur-X invoices, as UBL or UN/CEFACT CII XML or as a PDF with the XML embedded, and validates them against EN 16931 and the German XRechnung rules. It runs in Node.js, in serverless functions and in the browser. No Java, no external service, nothing leaves your machine.
Since 1 January 2025 every business in Germany has to be able to receive e-invoices, and creating them is a solved problem (libraries such as node-zugferd do it well). Checking what arrives is not: the reference validator of KoSIT is a Java application with Saxon and XSLT. Summand brings the same rules to JavaScript.
What you get
- The official rules, not a re-implementation. Summand ships the Schematron rules published by CEN/TC 434 (EN 16931 validation artefacts 1.3.16) and by KoSIT (XRechnung Schematron 2.6.0 for XRechnung 3.0) and runs them with its own XPath 2.0 and Schematron engine.
- UBL and CII: UBL 2.1 Invoice and CreditNote, UN/CEFACT Cross Industry Invoice D16B.
- PDF: extracts
factur-x.xml,zugferd-invoice.xmlorxrechnung.xmlfrom a ZUGFeRD / Factur-X PDF and compares the profile with the PDF's XMP metadata. - Profiles: recognises XRechnung 3.0 (standard, extension, CVD), EN 16931, Factur-X BASIC, EXTENDED, BASIC WL and MINIMUM, Peppol BIS Billing 3.0, and picks the right rules. The severity changes of the KoSIT configuration for XRechnung are applied as well.
- Clear results: every message has the rule id (
BR-CO-10,BR-DE-15), the severity, the XPath and the line in the XML, plus a summary of the invoice (number, date, parties, totals). - Leitweg-ID check for invoices to German public buyers.
- CLI for scripts and CI:
summand validate invoices/*.pdf. - No dependencies. About 90 KB gzipped including all rule sets.
How close is it to the official validator?
The test suite runs the official test material on every change:
| Test material | Result |
|---|---|
| CEN EN 16931 unit tests (1,142 expectations for UBL Invoice, UBL Credit Note and CII) | all pass |
| KoSIT XRechnung test suite (reference invoices, UBL and CII, standard, extension, CVD) | all valid |
| CEN example invoices (UBL and CII) | all valid |
What Summand does not do
Be clear about this when you build on it:
- No XML Schema (XSD) check yet. The KoSIT validator checks the document against the UBL or CII schema before the Schematron rules. Summand runs the Schematron rules only, so a misspelt element that no rule looks at goes unnoticed. This is on the roadmap.
- Not the reference implementation. For disputes, the KoSIT validator with the official configuration is authoritative. Summand aims to give the same result and is tested against the same material, but it is not certified.
- No Peppol BIS rules (PEPPOL-EN16931-R…) and no dedicated Factur-X EXTENDED rules yet. EXTENDED invoices are checked against EN 16931, with violations reported as warnings by default.
- No PDF/A check. Summand reads the embedded XML; whether the PDF itself is valid PDF/A-3 is not checked.
- No legal advice. A valid invoice under EN 16931 can still be wrong in content (wrong VAT rate, wrong buyer).
Pro
Summand Pro adds a readable invoice view with the validation report for inboxes and accounting, and batch validation with reports, duplicate detection and an audit trail.