Provide IssuerAssignedID exactly once

Error FX-SCH-A-000415 Factur-X

Element 'ram:IssuerAssignedID' must occur exactly 1 times.

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

IssuerAssignedID is missing from InvoiceReferencedDocument or occurs there more than once. The element must occur exactly once.

What the rule means

IssuerAssignedID contains the identifier assigned by the issuer to the referenced document. Exactly one element ensures that a single identifier value is provided.

Please provide `IssuerAssignedID` exactly once in the document reference

IssuerAssignedID is missing from InvoiceReferencedDocument or the element occurs more than once. You can adjust the document reference so that it occurs exactly once.

What to do
  1. Check InvoiceReferencedDocument for IssuerAssignedID.
  2. Make sure IssuerAssignedID is present exactly once.
  3. Generate the invoice again and validate it.
What it looks like
✗ Triggers the message 
<ram:InvoiceReferencedDocument>
  <ram:IssuerAssignedID>INV-123</ram:IssuerAssignedID>
  <ram:IssuerAssignedID>INV-456</ram:IssuerAssignedID>
</ram:InvoiceReferencedDocument>
✓ Correct 
<ram:InvoiceReferencedDocument>
  <ram:IssuerAssignedID>INV-123</ram:IssuerAssignedID>
</ram:InvoiceReferencedDocument>
Technical details

The test counts IssuerAssignedID elements in the InvoiceReferencedDocument context and requires the count to equal 1.

Where the rule applies

The rule applies to the InvoiceReferencedDocument reference in the settlement information.

Context (rule/@context)
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeSettlement/ ram:InvoiceReferencedDocument
Test expression (assert/@test)
count(ram:IssuerAssignedID)=1