The invoice-compliance engine for software with EU-bound invoices

Generate and validate XRechnung, Factur-X and Peppol BIS — with errors that teach the regulation. When a document fails you get the rule ID, the business term, what the rule requires and the fix, instead of a schematron assertion number.

1. The library

@attestwire/en16931 is an open-source TypeScript implementation of the EN 16931 semantic model and its national restrictions. JSON in, conformant XML out — or an invoice in, a list of teaching errors out. No network calls, no account, runs anywhere JavaScript runs.

pre-release · v0.1.0 Not on npm yet. The shapes below are the shipped shapes.

import { validateInput } from "@attestwire/en16931";

const result = validateInput({
  profile: "xrechnung-ubl",
  invoiceNumber: "2026-000142",
  issueDate: "2026-08-09",
  currency: "EUR",
  invoiceTypeCode: "380",
  seller: {
    name: "Acme GmbH",
    vatId: "DE123456789",
    address: {
      line1: "Chausseestr. 1",
      city: "Berlin",
      postalCode: "10115",
      countryCode: "DE",
    },
    electronicAddress: { schemeId: "0204", value: "04011000-1234512345-06" },
    contact: {
      name: "Buchhaltung",
      phone: "+49 30 1234567",
      email: "rechnungen@acme.example",
    },
  },
  buyer: {
    name: "Stadt Bonn",
    vatId: "DE987654321",
    address: {
      line1: "Berliner Platz 2",
      city: "Bonn",
      postalCode: "53111",
      countryCode: "DE",
    },
    electronicAddress: { schemeId: "0204", value: "04011000-1234512345-06" },
  },
  lines: [
    {
      id: "1",
      description: "Consulting, August 2026",
      quantity: 10,
      unitCode: "HUR",
      unitPrice: 150,
      vatCategory: "S",
      vatRate: 19,
    },
  ],
  payment: { meansCode: "58", iban: "DE02120300000000202051" },
  paymentTerms: "30 days net",
});

result.valid;      // false
result.errors[0];  // the object below

{
  "rule": "BR-DE-15",
  "field": "BT-10",
  "severity": "fatal",
  "message": "XRechnung requires a buyer reference (BT-10). For German public-sector buyers this is the Leitweg-ID; business buyers may supply any reference, but the field must be present.",
  "fix": "Ask your client for their Leitweg-ID (public sector) or an order/customer reference, and set buyerReference.",
  "example": "\"buyerReference\": \"04011000-1234512345-06\"",
  "xpath": "/ubl:Invoice/cbc:BuyerReference",
  "docsUrl": "https://attestwire.com/rules/BR-DE-15"
}

Every field there is load-bearing. rule and field are the identifiers your customer's tax adviser and their portal's rejection notice will use. message states the requirement, fix states the action, xpath points at the element in the generated document, and docsUrl resolves to a page on this site — the same URL whether the error surfaced in your CI, in a log line, or inside an agent's tool call.

58 rules are implemented and documented so far, across EN 16931 core, the German XRechnung CIUS and Peppol BIS 3. Browse the reference. Each page says where our check is stricter or looser than the published rule, because a validator you cannot calibrate is not much use.

2. The hosted API

The same engine behind an HTTP endpoint, for teams who would rather not run validation in their own stack: post an invoice, get the XML or the teaching errors back. Not open yet. Leave an address and we send one email when the beta opens — no drip sequence, no newsletter.

3. Free tools

Standalone utilities, no signup. They are plainly named because people arrive at them from a search, not from here.

• French E-Invoicing Checker live Look up any French company and check whether it is registered with an approved e-invoicing platform in the official DGFiP directory — every step explained in English.
• EU VAT number status building A VIES lookup that records the consultation number and the date, so you can evidence that a customer's VAT ID was valid on the day you invoiced. It will live at status.attestwire.com; it is not deployed, so this is deliberately not a link.

The dates that force this

Context, not urgency. Verify against the primary source before you plan a roadmap around any of them.

What this is not

Attestwire does not transmit invoices. We do not operate a Peppol access point, a French PDP or a KSeF connection, and we do not intend to — that is a regulated, capital-intensive business with different economics. We produce and check the document; your access point moves it. The library's output is shaped to be handed straight to one.