Developer preview · Early access
Validate and generate Factur-X, UBL 2.1 and CII invoices — EN 16931-compliant — through one JSON API. Built for SaaS, billing and POS products whose customers must meet France's 2026–2027 mandate and the wider EU wave.
POST /v1/validate · factur-x.pdf
{
"profile": "EN 16931 · Factur-X (EN profile)",
"result": "PASS",
"rules_checked": 142,
"warnings": ["BT-9: payment due date missing"]
}
Clause 1
Three endpoints cover the format work your team would otherwise build from a 400-page specification: strict validation with readable errors, generation from plain JSON, and conversion between syntaxes.
POST /v1/validate
Check a PDF or XML invoice against EN 16931 business rules and profile constraints. Every failure mapped to its BT/BG term, in plain English.
POST /v1/generate
Send invoice data as JSON, receive a compliant Factur-X PDF/A-3 or UBL 2.1 / CII XML — ready for your customer's accounts payable.
POST /v1/convert
Move between syntaxes — UBL to CII, XML to Factur-X PDF — without maintaining two mapping layers in your codebase.
Clause 2
Structured e-invoicing is becoming law across the EU. If your product issues invoices for businesses in these countries, these dates are your dates.
| Date | Jurisdiction | Obligation |
|---|---|---|
| 2026-01 | Belgium | B2B structured e-invoicing in force |
| 2026-09-01 | France | All companies must receive e-invoices; large & mid-size must issue |
| 2027-09-01 | France | SMEs and micro-enterprises must issue |
| 2027–2028 | Germany | Mandatory issuing rollout (XRechnung / ZUGFeRD) |
| 2030-07 | EU (ViDA) | Intra-EU B2B digital reporting & e-invoicing |
Clause 3
Invoices are business data. The API is designed so that yours never sit on our servers.
What this is, and is not. en16931.dev is a technical format layer — an independent developer tool for producing and checking EN 16931 documents. It is not a French Plateforme Agréée: it does not transmit invoices to the French public portal and does not perform e-reporting. It is not affiliated with CEN. Factur-X and ZUGFeRD are specifications of their respective owners.
Clause 4
Simple monthly plans, self-serve, cancel anytime. Early-access members lock the launch price.
$39 / month
$149 / month
Pricing shown for the early-access launch; document limits may be adjusted before general availability. Payments at launch will be handled by Paddle as merchant of record. A free tier for testing is planned.
Clause 5
Questions about formats, the mandate timeline, or fit for your product — write to hello@en16931.dev. Replies within two business days.