Validate CII Invoice using REST-API

Validate a UN/CEFACT Cross Industry Invoice (CII) XML document against the D16B schema and EN 16931 Schematron business rules. CII is the XML syntax used by ZUGFeRD, Factur-X, and many European e-invoicing networks — this endpoint verifies your standalone CII XML is fully compliant.

POST https://api.invoicexml.com/v1/validate/cii

Code Example

curl -X POST https://api.invoicexml.com/v1/validate/cii \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "[email protected]" \
  -F "version=2.3.2" \
  -F "profile=extended"

Try it out online — no coding required

Upload an invoice and get a full compliance report instantly, right in your browser.

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Request

Parameter	Type	Description
file *	binary	The invoice file to validate. Accepted format: standalone CII XML document.
version	string	Standard version (e.g. `2.3.2`). Defaults to the latest supported version.
profile	string	Compliance profile. Values: `minimum`, `basicwl`, `basic`, `en16931`, `extended`. Defaults to `en16931`.

Content-Type: multipart/form-data

Headers

Header	Value
Authorization *	Bearer YOUR_API_KEY
Content-Type	multipart/form-data

Response

200 The invoice is valid. Returns a JSON object confirming compliance.

Content-Type: application/json

{
  "valid": true,
  "detail": "Your invoice is cii compliant and meets the EN 16931 specifications.",
  "data": {
    "schemaValid": true,
    "schematronValid": true,
    "conformanceLevel": "EN16931"
  }
}

200 The invoice has validation errors. Returns a JSON object with structured error information.

{
  "valid": false,
  "detail": "Validation failed with 3 error(s)",
  "data": {
    "conformanceLevel": "EN16931"
  },
  "errors": {
    "xml": [
      "[BR-01] An invoice shall have a specification identifier.",
      "[BR-06] An invoice shall contain the seller name.",
      "[BR-08] An invoice shall contain the document total amount."
    ],
    "friendly": [
      {
        "rule": "BR-01",
        "line": null,
        "message": "The invoice is missing a specification identifier (BT-24)."
      },
      {
        "rule": "BR-06",
        "line": null,
        "message": "The seller must have a name (BT-27). Add the seller's name."
      },
      {
        "rule": "BR-08",
        "line": 2,
        "message": "Line item 2: The document total amount with VAT is missing or incorrect."
      }
    ]
  }
}

Error Reference

When an invoice fails validation, the errors.xml array contains one entry per violated business rule. Each entry starts with the rule identifier (e.g. [BR-01]) followed by the raw Schematron description.

The errors.friendly array provides a parallel set of user-facing messages — one object per violation. Each object contains:

Field	Type	Description
rule	string	The business rule identifier (e.g. `BR-01`, `BR-DE-15`).
line	int \| null	The 1-based invoice line item number the error relates to, or `null` when the error applies to the document level.
message	string	A plain-language explanation of the violation, suitable for displaying directly to end users.

Status	Meaning	Action
200	Validation completed. Check `valid` to determine compliance.	If `valid` is `false`, inspect `errors.xml` or `errors.friendly`.
401	Missing or invalid API key.	Check the `Authorization` header.
422	File is not a valid PDF or XML document.	Ensure you are uploading a supported file format.

Frequently Asked Questions

What is CII validation?

CII validation checks your Cross Industry Invoice XML against the UN/CEFACT D16B schema and the EN 16931 Schematron business rules. This ensures the document has the correct structure and satisfies all mandatory European invoicing requirements.

Should I use CII or UBL validation?

Use CII validation if your invoice follows the UN/CEFACT CII syntax — this is the format used inside ZUGFeRD and Factur-X files. Use EN 16931 validation if you want to validate the semantic model regardless of syntax.

Can I upload a ZUGFeRD PDF to this endpoint?

This endpoint expects a standalone CII XML file. If you have a ZUGFeRD or Factur-X PDF, use the /v1/validate/zugferd or /v1/validate/facturx endpoints — they extract the embedded XML automatically.

What CII schema version is validated against?

The validator uses CII D16B, which is the schema version referenced by EN 16931. This covers the CrossIndustryInvoice root element and all associated complex types.

Are CIUS-specific rules included?

The CII endpoint validates against the EN 16931 core rules. For country-specific CIUS rules (e.g., XRechnung, CIUS-FR), use the dedicated endpoints.