Hi Shaodi
please check the following
1. If you are clearing items across co codes, make sure the intercompany clearing accounts maintained in the configuration exist in the master data (FS00)
2. If you are using document splitting and maintained an account for profit center clearing , make sure the account exists in relevant co codes.
3. if there's a small difference between the amounts you are trying to clear, make sure the small differences clearing account exist in the relevant co codes.
Regards
Sach!n