Currency configuration of controlling area &1 is inconsistent.

What causes this issue?

Currency configuration of controlling area &V1& is inconsistent.
Controlling area &V1& is configured with currency type '30' ( =
currency of client )
and currency &V2&.
But the currency of the client is set to &V3&.

System Response

You cannot enter postings for FI or CO unless the currency configuration
is consistent for the assigned controlling area.

How to fix this error?

Change the configuration of <DS:TRAN.OKKP> currency of the controlling
area </> or the currency of the client.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.