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Warning

UBL-DT-12: Leave out the format attribute

In short

Warning: worth checking.

UBL-DT-12 means the invoice contains a format attribute, which the standard asks you to leave out. Remove the attribute wherever it occurs to clear the warning.

On this page

What it means

The check searches the whole file for a format attribute. In UBL it can occur on an embedded attachment (BT-125) to describe the format of the file. The MIME code (BT-125-1) and file name (BT-125-2) are separate attributes. This rule flags format wherever it occurs, not only on attachments.

Why it matters

EN 16931 asks you to omit format from UBL invoices and credit notes.

How to fix it

Remove the format attribute from every element that has it, or ask the supplier of your invoicing software to stop writing it. On embedded attachments, keep the mimeCode and filename attributes, which are required. If you build the XML yourself, check the whole file, including cbc:EmbeddedDocumentBinaryObject. Export again and recheck the file.

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

Format attribute should not be present

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-DT-12 still fails, and which other rules do.

Updated 6 November 2026