Date format required for the delivery note date

Error FX-SCH-A-001079 Factur-X

Attribute '@format' is required in this context.

Mandatory rule: As long as it is violated, the invoice is invalid and will be rejected by validators.
What is wrong

The @format attribute is missing from qdt:DateTimeString of the referenced delivery note. As a result, the date format is not specified.

What the rule means

The format attribute specifies how to read the date value in qdt:DateTimeString. It is needed to interpret the date unambiguously.

Please specify the date format for the referenced delivery note

The format is missing from qdt:DateTimeString of the delivery note. Add it so the date value can be read unambiguously.

What to do
  1. Add @format to qdt:DateTimeString of the delivery note.
  2. Enter the format code that corresponds to the date value.
  3. Regenerate the invoice and validate it again.
What it looks like
✗ Triggers the message 
<qdt:DateTimeString>20261003</qdt:DateTimeString>
✓ Correct 
<qdt:DateTimeString format="102">20261003</qdt:DateTimeString>
Technical details

The Schematron check requires the @format attribute to be present on the current qdt:DateTimeString element.

Where the rule applies

The rule applies to qdt:DateTimeString of the referenced delivery note in the delivery details of an invoice line.

Context (rule/@context)
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:IncludedSupplyChainTradeLineItem/ ram:SpecifiedLineTradeDelivery/ram:DeliveryNoteReferencedDocument/ram:FormattedIssueDateTime/ qdt:DateTimeString
Test expression (assert/@test)
@format