# ✅ Validate invoice file (FacturX, UBL, CII)

Validate an invoice file without submitting it for processing.

Supports validation of multiple e-invoicing formats:
- FacturX: Validates PDF structure and embedded XML against FacturX standards
- UBL: Validates XML against UBL schema
- CII: Validates XML against Cross Industry Invoice schema

All formats are checked for EN16931 compliance.
Returns detailed validation results with specific error messages and suggestions.

Endpoint: POST /invoicing/files/validate
Version: 1.0.0

## Header parameters:

  - `X-PDP-Client-Id` (string, required)
    ID of the PDP Client for which the operation is performed

## Request fields (multipart/form-data):

  - `file` (string, required)
    Invoice file (FacturX PDF, UBL XML, CII XML)

## Response 200 fields (application/json):

  - `is_valid` (boolean, required)
    Whether the invoice file is valid

  - `file_name` (string, required)
    Original file name

  - `file_size` (integer, required)
    File size in bytes

  - `detected_format` (any)
    Detected file format (FacturX, UBL, CII)

  - `format_version` (any)
    Detected format version

  - `pdf_valid` (boolean, required)
    Whether the PDF component is valid

  - `xml_valid` (boolean, required)
    Whether the XML component is valid

  - `issues` (array, required)
    List of validation issues found

  - `issues.field_path` (string, required)
    JSON path to the problematic field (e.g., 'seller.postal_address.country_code')

  - `issues.error_code` (string, required)
    Machine-readable error code (e.g., 'INVALID_COUNTRY_CODE')

  - `issues.error_message` (string, required)
    Human-readable error message

  - `issues.severity` (string, required)
    Issue severity: 'error', 'warning', or 'info'

  - `issues.suggested_value` (any)
    Suggested correct value if applicable

  - `total_errors` (integer, required)
    Total number of errors

  - `total_warnings` (integer, required)
    Total number of warnings

  - `extracted_data` (any)
    Extracted invoice data if validation succeeds

  - `en16931_invoice` (any)
    Complete EN16931-compliant invoice if validation succeeds

  - `summary` (string, required)
    Human-readable validation summary

## Response 400 fields (application/json):

  - `error` (string, required)

  - `code` (integer, required)

  - `trace_id` (string, required)

## Response 401 fields (application/json):

  - `error` (string, required)

  - `code` (integer, required)

  - `trace_id` (string, required)


## Response 422 fields