Company code & does not exist

What causes this issue?

If the <GL:assignment_control>assignment control</> indicator has the
value 1, you cannot freely select the controlling area key. This is
taken automatically from the company code key. However, since company
code &V1& does not exist, you cannot create controlling area &V1&. If
controlling area &V1& already exists, you cannot reset the indicator to
1.

How to fix this error?

If the indicator is set to 1, create controlling areas only with the
same keys as existing company codes.

Error message extract from SAP system. Copyright SAP SE.