Public REST API

fakturai invoice API

Generate technically checked EN 16931 ZUGFeRD / Factur-X invoice PDFs from automation tools and backend services.

Endpoint

POST https://fakturai.de/api/v1/invoices
X-API-Key: <FACTURAI_API_KEY>
Content-Type: application/json
Accept: application/pdf

Successful requests return 201 application/pdf. Errors return JSON with error and detail fields.

Request Body

The seller profile is attached to the API key. Send buyer, dates, currency, and invoice line items.

{
  "invoice_date": "2026-06-01",
  "due_date": "2026-06-15",
  "currency": "EUR",
  "buyer": {
    "name": "Acme GmbH",
    "address": {
      "line_one": "Beispielweg 42",
      "postcode": "80331",
      "city": "Muenchen",
      "country": "DE"
    },
    "vat_id": "DE123456789",
    "contact_email": "buchhaltung@example.com"
  },
  "lines": [
    {
      "name": "Software development",
      "description": "Implementation work",
      "quantity": "8",
      "unit": "HUR",
      "unit_price": "150.00",
      "vat_rate": "19.00"
    }
  ],
  "number_prefix": "RE-2026"
}

Schema

Machine-readable schema: https://fakturai.de/schemas/invoice-input/v1.json

Status Codes

Status	Meaning
`201`	Invoice generated and returned as a PDF.
`400`	Invalid JSON.
`401`	Missing or invalid API key.
`402`	Free-tier invoice limit exhausted.
`422`	Payload failed format or compliance validation.
`503`	Invoice generation service unavailable.

Agent Discovery

Agent-facing summary: https://fakturai.de/llms.txt. Remote MCP endpoint: https://fakturai.de/mcp.

Validator

The free invoice validator is reachable at https://fakturai.de/en/validator.