Field & is not allowed for incompleteness in area &

What causes this issue?

You have attempted to enter field name &V1& in the control for
incompleteness of the document fields in foreign trade. This field name
is not allowed for area &V2& or it does not exist.

System Response

The system does not allow this entry.

How to fix this error?

Enter a valid field name.

Error message extract from SAP system. Copyright SAP SE.