Create Factur-X Invoice using REST-API

Totals and tax breakdown are omitted — the API calculates them automatically from the line items.

curl -X POST https://api.invoicexml.com/v1/create/facturx \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "InvoiceNumber=INV-2025-001" \
  -F "IssueDate=2025-07-01" \
  -F "PaymentDueDate=2025-08-01" \
  -F "Currency=EUR" \
  -F "SellerName=Acme GmbH" \
  -F "SellerTaxId=DE123456789" \
  -F "SellerStreet=Musterstr. 1" \
  -F "SellerPostcode=10115" \
  -F "SellerCity=Berlin" \
  -F "SellerCountry=DE" \
  -F "BuyerName=Example Corp" \
  -F "BuyerStreet=12 Rue de Rivoli" \
  -F "BuyerPostcode=75001" \
  -F "BuyerCity=Paris" \
  -F "BuyerCountry=FR" \
  -F "Lines[0].Description=Consulting Services" \
  -F "Lines[0].Quantity=10" \
  -F "Lines[0].UnitPrice=150.00" \
  -F "Lines[0].TaxPercentage=19" \
  -F "PaymentMeansCode=30" \
  -F "IBAN=DE89370400440532013000" \
  -o invoice-facturx.pdf

Request

Submit invoice data as multipart/form-data. All monetary values use decimal format (e.g. 1234.56). Totals and tax breakdown are auto-calculated when omitted — only line items are required.

Document

Seller

Buyer

Payment

Line Items

Submit one or more line items using indexed field names: Lines[0].Description, Lines[1].Description, etc. At least one line item is required.

Totals (auto-calculated when omitted)

All totals are rounded to 2 decimal places. If provided, your values are used as-is (still rounded). If omitted, they are calculated from the line items.

Tax Breakdown (auto-generated when omitted)

When omitted entirely, the array is auto-generated by grouping Lines[] on (TaxCategoryCode, TaxPercentage). Only required if you provide the breakdown manually.

Standard-specific Requirements

Some fields are only required for specific output standards. Fields not listed here follow the rules in the tables above.

✓* = required but auto-defaulted from another field when omitted.

XRechnung Fields (optional for other standards)

The following fields are required for XRechnung and optional for all other standards. When not provided, some fields are auto-defaulted from other values.

Seller Contact (BG-6)

Electronic Addresses

Options

Headers

Response

{
  "type": "https://tools.ietf.org/html/rfc9110#section-15.5.1",
  "title": "Model Validation Failed",
  "status": 400,
  "errorCode": 4002,
  "detail": "One or more fields are invalid.",
  "errors": {
    "SellerName": ["Seller name is required."],
    "Lines[0].Description": ["Line item description is required."]
  }
}

{
  "type": "https://tools.ietf.org/html/rfc9110#section-15.5.1",
  "title": "XML Validation Failed",
  "status": 400,
  "errorCode": 4001,
  "detail": "The generated invoice contains 2 validation error(s).",
  "errors": {
    "xml": [
      "[BR-CO-15] Invoice total amount with VAT = 1785.00 expected 1500.00 + 285.00.",
      "[BR-S-08] VAT category tax amount must equal category basis × rate."
    ],
    "friendly": [
      {
        "rule": "BR-CO-15",
        "line": null,
        "message": "The invoice total with VAT does not match. Expected 1500.00 + 285.00 = 1785.00."
      },
      {
        "rule": "BR-S-08",
        "line": null,
        "message": "The VAT breakdown for Standard rate must have a positive taxable amount and the correct rate. Check the tax breakdown."
      }
    ]
  }
}

Error Reference

Errors are returned as RFC 7807 ProblemDetails. The errorCode field indicates the error category.

Frequently Asked Questions