Referencing at header level not permitted for this scenario

What causes this issue?

Referencing at header level not permitted for this scenario

System Response

You are passing a reference document at header level that does not exist
at the item level. However this scenario is not supported.

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.