Dear Huy,
Regarding the error you mentioned KD256 in KO88/CO88, there is a SAP
note 179533 talking about this error in quite details especially a part:
The principle is that settlement
compares the settlement date (last day of settlement period) with the
date where TECO has been set. If Settlement date > date of TECO, then
actual cost will be settled. The TECO date can be checked in table field
AUFK-IDAT2. I guess, the period is different from the one you used in
KO88.
Thanks a lot.
Best regards,
Jason