Conformo

Free, client-side invoicing that produces the legally valid electronic invoice your country actually requires — not just a good-looking PDF.

Open the app · Validate an invoice you already have · Docs: which countries require this

No signup, no account, no server — everything runs in your browser and your invoice data never leaves your machine unless you choose to send it somewhere.

Why this exists

France, Germany, Belgium, Poland and Italy now require — or are phasing in — a structured electronic invoice, not a document that merely looks like one. A PDF, however good-looking, is not one of those anymore. Most invoicing tools stop at the PDF.

Conformo builds the EN 16931 semantic model first, then serializes it to whatever your country actually needs, and embeds that structured data inside a PDF/A-3 so a human still gets something readable. It validates the result live against the official CEN Schematron and each country's own rules, and shows you the result instead of just asserting it.

Related MCP server: Fintom8 E-Invoice MCP Server

Formats supported

• Factur-X / ZUGFeRD (CII) — France and Germany

• UBL 2.1 (Invoice and Credit Note)

• XRechnung 3.0 — Germany's public-sector format, both CII and UBL

• Peppol BIS Billing 3.0 — the cross-border network used across the EU

• PDF/A-3b with the structured XML embedded, for every format above

Every format passes its official XSD and the EN 16931 Schematron; the country-specific layers (KoSIT for XRechnung, Peppol BIS for Peppol, the French CTC rules) are validated on top of that, never instead of it.

Get started

As an app — see the links above, or run it yourself with Docker:

docker compose up --build   # then open http://localhost:8080

As a library (npm):

npm install @conformo/core @conformo/formats

import { buildCII } from '@conformo/formats';

const invoice = {
  number: 'INV-2026-0001',
  typeCode: '380',
  issueDate: '2026-09-20',
  currency: 'EUR',
  seller: { name: 'Northwind Studio SARL', vatId: 'FR32123456789', street: '12 Rue Exemple', city: 'Paris', postcode: '75004', country: 'FR' },
  buyer: { name: 'Handelsgesellschaft Muster GmbH', vatId: 'DE123456789', street: 'Hauptstrasse 8', city: 'Berlin', postcode: '10115', country: 'DE' },
  lines: [{ name: 'Website design', quantity: 1, unitPriceMinor: 480000, unitCode: 'C62', taxCategory: 'S', taxRate: 20 }],
};

const xml = buildCII(invoice); // Factur-X/ZUGFeRD CII XML, ready to embed in a PDF/A-3

Money is always integer minor units (cents) — never floats — so the totals never drift by the cent that gets an invoice rejected.

As a CLI:

npx @conformo/cli validate my-invoice.xml --country FR
npx @conformo/cli parse an-invoice.pdf --csv out.csv

As an MCP server (for agents that need to issue or check invoices):

{
  "mcpServers": {
    "conformo": { "command": "npx", "args": ["-y", "@conformo/mcp-server"] }
  }
}

Exposes create_invoice, validate_invoice, and convert_invoice over stdio.

Which countries require this

Generated from a sourced, versioned dataset — every row cites a tax authority, ministry, or official EU source, or is marked unverified.

Full detail per country, generated from the same dataset, is at conformo-docs.vercel.app.

Anti-goals

This is not, and will not become, accounting, payroll, expense, inventory, CRM, or project/time-tracking software, and it will never require an account or a server. If that's what you need, Akaunting and Dolibarr already do it well.

Contributing / building from source

See docs/DEVELOPMENT.md to build, test, or run this repo yourself, and CONTRIBUTING.md for the project's non-negotiable invariants.

License

Apache-2.0.