PDF to CII Transformation API Reference

Convert a PDF invoice into a standalone UN/CEFACT Cross Industry Invoice (CII) XML document. CII is the XML syntax that underpins both ZUGFeRD and Factur-X and is one of the two official syntaxes of the European EN 16931 standard.

This is an experimental feature. AI can make mistakes. Always double-check the result before submitting it to tax authorities.

POST https://api.invoicexml.com/v1/transform/to/cii

Code Example

curl -X POST https://api.invoicexml.com/v1/transform/to/cii \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "[email protected]" \
  -F "language=en"

Try it out online, no coding required

Upload a PDF and get a compliant invoice back instantly, right in your browser.

Try It Online

Request

Parameter	Type	Description
file *	binary	The invoice file to process.
language	string	Language for PDF labels and date formatting. Values: `en`, `de`, `fr`. Defaults to `en`.

Content-Type: multipart/form-data

The source and target formats are part of the endpoint path, and everything else (syntax, declared profile, specification identifier) is read from the document itself, so there is nothing more to configure.

Headers

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

Response

200 Converted invoice

Returns the CII XML document.

Content-Type: application/xml

Frequently Asked Questions

What is CII?

CII (Cross Industry Invoice) is an XML schema maintained by UN/CEFACT. It is one of the two syntaxes allowed by the European e-invoicing standard EN 16931, the other being UBL 2.1.

When should I use CII instead of UBL?

CII is the default syntax for ZUGFeRD and Factur-X invoices. Use CII when your trading partners or national regulations (e.g., Germany, France) expect CII-based documents.

Is the output embedded in a PDF?

No. This endpoint returns a standalone CII XML file. If you need the XML embedded inside a PDF/A-3, use the /v1/transform/to/facturx or /v1/transform/to/zugferd endpoints instead.

Is the XML validated?

Yes. Every generated CII document is validated against EN 16931 Schematron business rules before delivery to ensure compliance.

What CII version is used?

The API generates CII D16B (the version referenced by EN 16931), ensuring compatibility with all European e-invoicing infrastructure.