UBL-SR-51:An address can only have one third line.
Fix: Duplicate address line 3. An address can have at most one additional address line (third line).
Duplicate address line 3. An address can have at most one additional address line (third line).
Engine Classification
Requires user confirmation before application
What is UBL-SR-51?
UBL-SR-51 is a fatal validation rule defined in the EN16931 specification. It validates the AddressLine 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: //cac:PostalAddress/cac:AddressLine
Why This Error Matters
Invoice will be rejected by EN16931 validators. These structural rules enforce cardinality and conditional requirements. Fix the duplicate element or provide the required companion element.
UBL-SR-51 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-51
- ·Specification: EN16931
How to Fix It
Locate the duplicate entries
Search for multiple cac:AddressLine elements at //cac:PostalAddress/cac:AddressLine. Only one instance is allowed per the specification.
Remove the duplicates
Duplicate address line 3. An address can have at most one additional address line (third line).
Re-validate your invoice
Upload the corrected invoice to confirm UBL-SR-51 is resolved.
XML Example
Generic example based on the rule's target XPath. Your actual XML structure may differ.
<!-- Required block is missing --> <!-- <cac:AddressLine> ... </cac:AddressLine> -->
<!-- Add the required block --> <cac:AddressLine> <!-- child elements --> </cac:AddressLine>
Technical Reference
//cac:PostalAddress/cac:AddressLineCommon Causes
- ·Address contains multiple AddressLine/Line elements
- ·Only one cbc:AdditionalStreetName or one third line allowed
- ·Address line 3 appears more than once
- ·Duplicate third address line in postal address
- ·ERP exports multiple AddressLine elements
Seeing this in production? The API handles UBL-SR-51 automatically. See the fix response →
Frequently Asked Questions
Duplicate address line 3. An address can have at most one additional address line (third line).
Duplicate address line 3. An address can have at most one additional address line (third line). You can also use Invoice Navigator's compliance engine to correct this automatically in your pipeline.
Yes, UBL-SR-51 is a critical error that will cause invoice rejection. It must be fixed before submission.
Many instances of UBL-SR-51 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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