Higher-level items not allowed

What causes this issue?

In the IDoc, bills of material are sent as subordinate items for an
invoice item. The system does not recognize these as being subordinate,
and tries to invoice the same items twice.
You can identify subordinate items by the fact that there is a value in
the field UEPOS in segment E1EDP01.
EDI invoice receipt in Materials Management cannot process IDocs
containing bills of material.

System Response

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.