E‑Rechnungs-Studio

NormAPI is an e-invoicing API for software teams that issue or check German e-invoices in the XRechnung and ZUGFeRD formats. It has two endpoints. Validation checks an invoice (UBL, CII or ZUGFeRD PDF) against the official KoSIT rule set and returns every finding as JSON, with its rule code, severity and location in the document. Generation turns invoice data sent as JSON into a validated XRechnung (UBL or CII) or ZUGFeRD PDF. Rule-set updates are included: KoSIT publishes a new version roughly every six months, and the version in force is reported with every result. A TypeScript client is available on npm. The same validation runs in a free browser validator that needs no sign-up and never stores invoice content, and 137 of the 307 rules have a plain-language reference page explaining what they mean and how to fix them. Validation is free. Generation costs EUR 49 a month for 500 invoices or EUR 149 for 2,500, and an account includes 25 generated invoices a month for free.

InvoiceXML is an API-first platform for European e-invoice compliance. A single REST API generates, validates, and converts every major format covered by EN 16931: Factur-X, ZUGFeRD, XRechnung, UBL, and CII. Generation accepts clean JSON input and returns a compliant XML document, or a PDF/A-3 hybrid invoice with the XML embedded according to format-specific rules. Validation runs the official Schematron rulesets, and returns structured results plus user-friendly plain-language explanations alongside the raw rule output. Format conversion (POST /v1/convert/{from}/to/{format}) maps any supported format to any other through a canonical internal representation. A separate /v1/transform/ namespace handles AI-assisted extraction from legacy PDF invoices into structured XML. No-Code integrations expose the core operations to non-developers. MCP server provides the compliance toolkit for AI Agentic workflows. Always up to date with the latest standard requirements - zero maintenance.