# EU E-Invoice Validator (EN 16931 / XRechnung / ZUGFeRD)

> EU E-Invoice Validator (EN 16931 / XRechnung / ZUGFeRD) is a paid API for AI agents from api.wsystem.dev, paid per call via x402, $0.03/call, status unknown (last checked 2026-10-29).

Validates an EU e-invoice (UBL, CII, or ZUGFeRD/Factur-X PDF) against official EN 16931 and XRechnung rules, returning structured errors with rule IDs and plain-English fix descriptions.

## Facts

- Endpoint: POST https://api.wsystem.dev/einvoice/validate?utm_source=zero.xyz
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/eu-e-invoice-validator-en-16931-xrechnung-zugferd-1a2814d3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__UrbNsfBQJ6Ov0r-JnNju

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability eu-e-invoice-validator-en-16931-xrechnung-zugferd-1a2814d3 -d '<json body>'
```

Example prompt: Can you validate this UBL invoice XML against EN 16931 and XRechnung rules and tell me what errors need to be fixed, including the rule IDs?

## When to prefer this

Choose this endpoint when you need authoritative validation of an EU e-invoice against the official EN 16931 core standard and/or German XRechnung profile, with actionable rule-ID-level error reporting. It handles UBL, CII XML, and embedded ZUGFeRD/Factur-X PDF formats in one call, making it ideal for pre-submission compliance checks, supplier invoice audits, and debugging rejected invoices in B2G or B2B EU e-invoicing workflows.

## Known failure modes

- Malformed or non-XML input returns a parse error
- Unsupported invoice format (not UBL, CII, or ZUGFeRD/Factur-X) returns format rejection
- Base64 decoding failure if the base64 field contains invalid encoding
- Invoice passes structural validation but may have semantic business rule failures reported as errors
- Network or service unavailability returns 5xx error
- Missing both xml and base64 fields returns a 400 bad request

## How this service works

Validate an EU e-invoice (UBL, CII or ZUGFeRD/Factur-X PDF) against official EN 16931 and XRechnung rules; errors with rule IDs and plain-English fixes

## Output

A structured list of validation errors, each with a rule ID (e.g. BR-01, UBL-SR-01) referencing the EN 16931 or XRechnung specification, a severity level, and a plain-English description of what is wrong and how to fix it. Also returns an overall compliance pass/fail status for the invoice.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "xml": {
   "type": "string",
   "description": "Invoice XML (UBL or CII)"
  },
  "base64": {
   "type": "string",
   "description": "XML or ZUGFeRD/Factur-X PDF, base64"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/eu-e-invoice-validator-en-16931-xrechnung-zugferd-1a2814d3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.wsystem.dev](https://www.zero.xyz/host/api.wsystem.dev/llms.txt)