Engine Classification
Financial or legal field · Modification blocked by policy
Reason: ATCUD (Código Único de Documento) requires a validation series registered with Autoridade Tributária. The code must be algorithmically generated by certified invoicing software using the registered series. You cannot manually add an ATCUD - ensure your invoicing software is AT-certified and has a valid series registered.
What is PT-R-004?
PT-R-004 is a fatal validation rule defined in the ubl-2.1 specification (PRT national rules). It validates the XPath: Extension or Note for ATCUD element in the UBL invoice XML.
When this rule fires, the invoice is rejected by Peppol access points and never reaches the buyer.
Target path: XPath: Extension or Note for ATCUD
Why This Error Matters
ATCUD required for Portuguese invoice validity.
PT-R-004 is a hard failure — the invoice must be corrected and re-sent before it can reach the recipient.
Validator Behavior
- ·Causes invoice rejection
- ·Fails UBL schema validation
- ·Error returned: PT-R-004
- ·Specification: ubl-2.1
How to Fix It
Get ATCUD series
Register series with AT
Generate code
Series + document number
Add to invoice
Include ATCUD in document
XML Example
Generic example based on the rule's target XPath. Your actual XML structure may differ.
<!-- Triggers validation error --> <XPath: Extension or Note for ATCUD></XPath: Extension or Note for ATCUD>
<!-- Corrected --> <XPath: Extension or Note for ATCUD>VALID_VALUE</XPath: Extension or Note for ATCUD>
Technical Reference
XPath: Extension or Note for ATCUDCommon Causes
- ·Missing ATCUD
- ·Invalid ATCUD format
- ·Uncertified software
Seeing this in production? The API handles PT-R-004 automatically. See the fix response →
Frequently Asked Questions
Portuguese invoices require ATCUD (unique document code).
Add ATCUD code from certified software. This error involves a protected field — Invoice Navigator flags it in your pipeline so your team can correct it at the source.
Yes, PT-R-004 is a critical error that will cause invoice rejection. It must be fixed before submission.
Related Errors
Related Content
Last updated: 3 March 2026
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