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Warning

UBL-CR-135: A project reference should not carry an issue date

In short

Warning: worth checking.

UBL-CR-135 means the project reference in your UBL file has an issue date (cbc:IssueDate), which EN 16931 does not use. Keep the project reference itself and remove the date.

On this page

What it means

The project reference (BT-11) is cbc:ID inside cac:ProjectReference. This rule checks that a document-level cac:ProjectReference in a UBL invoice or credit note does not also contain cbc:IssueDate. It does not check the invoice date (BT-2), which is directly under Invoice or CreditNote.

Why it matters

EN 16931 does not use a separate issue date within the project reference.

How to fix it

Remove cac:ProjectReference/cbc:IssueDate and keep cac:ProjectReference/cbc:ID. Do not remove the invoice date (BT-2), which sits directly under the Invoice or CreditNote element. Export the corrected file and check it again.

Once the file is corrected, check it again for free: Validate an invoice against EN 16931

Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice

The rule as published

A UBL invoice should not include the ProjectReference IssueDate

Where this rule applies

Rule set Version
EN 16931 (UBL) 1.3.17
EN 16931 (UBL credit note) 1.3.17
XRechnung 3.0 (UBL) 3.0.2
XRechnung 3.0 (UBL credit note) 3.0.2
Peppol BIS Billing 3.0 (invoice) 2026.5
Peppol BIS Billing 3.0 (credit note) 2026.5
SI-UBL 2.0 / NLCIUS (invoice) 2.0.3.13
SI-UBL 2.0 / NLCIUS (credit note) 2.0.3.13
France CTC (UBL invoice) 1.4.0-04
France CTC (UBL credit note) 1.4.0-04
CIUS-RO UBL Invoice 1.0.9 1.0.9
CIUS-RO UBL Credit Note 1.0.9 1.0.9
Rule text from phive-rules 4.6.4.

Check your file

Drop your e-invoice to see whether UBL-CR-135 still fails, and which other rules do.

Updated 6 November 2026