Message type: E = Error
Message class:  FKKBIX - Conv.Inv.: Billing (Invoice Preprocessing) 
Message number: 603
Message text: No subprocess found for discount/charge key &1 account assignment grp &2
The system could not determine a subprocess for <DS:DE.DISCKEY_KK>
discounts or charges</> &V1& and <DS:DE.DISC_ASSGR_KK>account assignment
group </> &V2&.
The system issues an error message and will not allow you to continue with this transaction until the error is resolved.
Check the system settings.
INCLUDE FICA_NA_CUST_2 OBJECT DOKU ID TX
Error message extract from SAP system. Copyright SAP SE.
The SAP error message FKKBIX603 indicates that the system could not find a subprocess for a specific discount or charge key associated with a given account assignment group. This error typically arises in the context of financial transactions, particularly when dealing with billing or invoicing processes.
Cause: Missing Configuration: The most common cause of this error is that the discount or charge key specified in the transaction is not properly configured in the system. This could mean that the key does not exist or is not linked to the appropriate account assignment group. Incorrect Account Assignment Group: The account assignment group specified in the error message may not be correctly set up to handle the discount or charge key in question. Data Inconsistencies: There may be inconsistencies in the master data or transaction data that lead to the system being unable to find the necessary subprocess.
Solution: Check Configuration: Go to the configuration settings for discounts and
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
FKKBIX602 No class found for discount/charge key &1 account assignment group &2
What causes this issue?  The system could not find a class for the base items of <DS:DE.DISCKEY_KK>discount or charge</> &V1& and ...
FKKBIX601 Account assignment group &1 not found for discounts and charges
What causes this issue?  The system could not find <DS:DE.DISC_ASSGR_KK>account assignment group </> &V1&.System Response  The sys...
FKKBIX604 No billable item type found for disc/charge key &1 acct assignment grp &2
What causes this issue?  The system could not determine the billable item type for <DS:DE.DISCKEY_KK>discount/charge</> &V1& and &...
FKKBIX605 Base item could not be created in class &1
What causes this issue?  You want to use <DS:DE.BITCAT_KK>billable item class</> &V1& for storing the base items for <DS:DE.DIS...
Click on this link to search all SAP messages.