E-Invoicing API | ZUGFeRD & Factur-X | thelawin.dev

thelawin.dev is a Micro SaaS for EU-compliant e-invoicing. Send JSON via REST API, get a valid PDF/A-3 with embedded XML back.

Do you have a service or library somewhere in your infrastructure that creates PDF invoices from your data but isn't ready for EN 16931? thelawin.dev is your drop-in replacement.

The EU mandates electronic invoicing for B2G (business-to-government) and increasingly B2B transactions. Germany: B2G since 2020, B2B receiving from Jan 2025, issuing from 2027. France: Sept 2026/2027. Italy: since 2019.

Think of the XML attachment as a "digital package insert" for your invoice: machine-readable, legally compliant, and required for doing business in the EU.

Anyone who generates invoices programmatically:

• Enterprises – replace complex on-premise PDF libraries
• SaaS providers – add compliant invoicing to your platform
• Freelance developers – simple API, no infrastructure to maintain
• AI agents – native MCP support for Claude and other LLMs

The Micro SaaS approach means pay only for what you use, from 0 to 2,000+ credits per month.

We don't store it. Ever. thelawin.dev is truly stateless:

• Your invoice data is processed entirely in RAM
• PDF is generated and returned immediately as Base64
• Nothing is written to disk, no database storage
• Only usage counters (no content) are logged for billing

Billing via Paddle.com (Merchant of Record) handles EU VAT so we never touch payment data.

9 EU-compliant formats from a single JSON input:

Use "format": "auto" and we'll pick the right one based on the country codes.

One POST request. That's it.

• Test client built into this website – try before you code
• 8 official SDKs – TypeScript, Python, Ruby, Kotlin, Java, Swift, Dart, C#
• Install: gem install thelawin (Ruby on RubyGems), all others via GitHub
• OpenTelemetry support for monitoring and tracing
• MCP server for AI agent integration
• Discord – join the developer community for questions and support

Most people have it running within an hour.

Yes, forever. The Sandbox plan is free for testing and integration.

• Full API access to all 9 formats
• /validate is always free (no credits consumed)
• Demo key for unlimited watermarked PDFs
• Buy credit packs (€4.90 / 100 credits) for production PDFs without watermark
• Or upgrade to Starter/Pro for monthly credits

E-Rechnungspflicht timeline:

• Jan 2025: all German businesses must be able to receive e-invoices
• Jan 2027: large businesses must send e-invoices (B2B)
• Jan 2028: all businesses must send e-invoices

thelawin.dev supports both ZUGFeRD (B2B) and XRechnung (B2G), so you stay compliant either way.

Yes. Every XRechnung invoice generated by thelawin.dev is validated against the official KoSIT Schematron rules (Koordinierungsstelle für IT-Standards).

That's the check German government portals like ZRE (Zentrale Rechnungseingangsplattform) and OZG-RE run on submitted invoices, so a KoSIT pass here usually means acceptance there.

Yes. We generate Factur-X 1.0.8 invoices that are fully compatible with the French B2G portal Chorus Pro.

Heads-up: France introduces mandatory e-invoicing (facturation électronique) in September 2026 for large enterprises, with full B2B coverage by 2027.

thelawin.dev generates PDF/A-3 with embedded CII XML, meeting all Factur-X EN 16931 profile requirements.

Yes. thelawin.dev supports FatturaPA 1.2.2 with all the required fields for submission to the SDI (Sistema di Interscambio).

We handle the Italian-specific requirements:

• Codice Destinatario – 7-character recipient code
• Codice Fiscale – Italian tax ID
• Partita IVA – VAT number formatting
• PEC – certified email address