Company code & is not defined as an organization unit

What causes this issue?

The selected company code was not created as an organization unit, or it
has been deleted.

System Response

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

How to fix this error?

The company code is not defined as an organization unit. Either
delete this company code from the assignment or set up the company code
again.
To set up the company code, proceed as follows:
<DS:TRANS.OX02>Set up the company code</> as a new organization unit
<DS:TRANS.OBY6>Assign values to the company code</>
<DS:TRANS.OMR8>Set the purchase order text indicator</> for the
purchase order supplement.
Once the error has been removed, start the transaction again.

Error message extract from SAP system. Copyright SAP SE.