Is UBL-SR-42 a critical error?

Yes, UBL-SR-42 is a critical error that will cause invoice rejection. It must be fixed before submission.

Can UBL-SR-42 be automatically fixed?

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.

errorEN16931

`UBL-SR-42`:Party tax scheme shall occur maximum twice in accounting supplier party

Your seller party (AccountingSupplierParty) contains more than two PartyTaxScheme elements. EN16931 allows maximum two (one VAT scheme and optionally one other tax scheme).

Severity

Fatal

Rule set

EN16931

Country

All EU

Fix type

CONFIRM

Confidence

85%

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 non-compliant and will be rejected by Peppol access points and national validation services. The sending system receives a rejection response and the invoice does not reach the buyer.

Target path: /Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme

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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. Invoices that trigger this rule are rejected at the access point and never reach the recipient. In Peppol networks, this means your sending system receives an MLR (Message Level Response) with a rejection status. The invoice must be corrected and re-sent, adding delay to your payment cycle.

Validator Behavior

·Causes invoice rejection
·Fails EN 16931 business rule validation
·Error returned: UBL-SR-42
·Specification: EN16931

XML Example

Generic example based on the rule's target XPath. Your actual XML structure may differ.

Before

<!-- Required block is missing -->
<!-- <cac:PartyTaxScheme> ... </cac:PartyTaxScheme> -->

After

<!-- Add the required block -->
<cac:PartyTaxScheme>
  <!-- child elements -->
</cac:PartyTaxScheme>

Technical Reference

XPath/Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme

SpecEN16931

Operationremove_duplicates

StrategyRemove excess party tax scheme entries beyond the allowed maximum of two, keeping first two

Common 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 →

Handle UBL-SR-42 Automatically in Your Pipeline

The compliance engine auto-remediates this error with controlled safety policies and evidence pack generation.

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UBL-SR-42:Party tax scheme shall occur maximum twice in accounting supplier party