Error while running Internal Order Settlement (KO88)

Hi,

We are in ECC 6. We are facing an error while settling one internal order using T.Code KO88.

The error message says :

Execute amount settlement up to and including settlement period 001 2009 first

Message KD262

We have already settled the internal order upto previous month. But, we are unable to settle the order for the current month.

Any suggestion please.

Regards,

Ganesan