UBL-SR-42:Party tax scheme shall occur maximum twice in accounting supplier party
Fix: Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme).
Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme).
Engine Classification
Requires user confirmation before application
What is UBL-SR-42?
UBL-SR-42 is a fatal validation rule defined in the EN16931 specification. It validates the PartyTaxScheme element under AccountingSupplierParty > Party in the UBL invoice XML.
When this rule fires, the invoice is rejected by Peppol access points and never reaches the buyer.
Target path: /Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme
Why This Error Matters
Invoice will be rejected by EN16931 validators. Only VAT identifier and one additional tax scheme are permitted per seller.
UBL-SR-42 is a hard failure — the invoice must be corrected and re-sent before it can reach the recipient.
Validator Behavior
- ·Causes invoice rejection
- ·Fails EN 16931 business rule validation
- ·Error returned: UBL-SR-42
- ·Specification: EN16931
How to Fix It
Locate the duplicate entries
Search for multiple cac:PartyTaxScheme elements at /Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme. Only one instance is allowed per the specification.
Remove the duplicates
Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme).
Re-validate your invoice
Upload the corrected invoice to confirm UBL-SR-42 is resolved.
XML Example
Generic example based on the rule's target XPath. Your actual XML structure may differ.
<!-- Required block is missing --> <!-- <cac:PartyTaxScheme> ... </cac:PartyTaxScheme> -->
<!-- Add the required block --> <cac:PartyTaxScheme> <!-- child elements --> </cac:PartyTaxScheme>
Technical Reference
/Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyTaxSchemeCommon Causes
- ·ERP exports all tax registrations instead of just VAT and one other
- ·Multiple country tax schemes exported when only two allowed
- ·Template includes extra PartyTaxScheme elements
- ·Data migration added duplicate tax scheme entries
- ·Manual XML editing introduced extra tax schemes
Seeing this in production? The API handles UBL-SR-42 automatically. See the fix response →
Frequently Asked Questions
Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme).
Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme). You can also use Invoice Navigator's compliance engine to correct this automatically in your pipeline.
Yes, UBL-SR-42 is a critical error that will cause invoice rejection. It must be fixed before submission.
Many instances of UBL-SR-42 can be automatically corrected using Invoice Navigator's compliance engine. The fix is applied in your pipeline with full audit evidence.
Related Content
Last updated: 14 April 2026
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