Message type: E = Error
Message class:  FKKEXC - Message Class for External Payments 
Message number: 084
Message text: Withdrawal &1 entered for branch &3, cash desk &2 exists already
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
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The SAP error message FKKEXC084 indicates that there is an attempt to enter a withdrawal for a specific branch and cash desk combination that already exists in the system. This typically occurs in the context of financial transactions, particularly in the area of contract accounts receivable and payable (FI-CA).
Cause: The error is triggered when: A withdrawal transaction is being processed for a branch and cash desk combination that has already been recorded in the system. There may be duplicate entries or an attempt to process the same transaction multiple times.
Solution: To resolve this error, you can take the following steps: Check Existing Transactions: Review the existing transactions for the specified branch and cash desk combination. You can do this by navigating to the relevant transaction history or logs in SAP. Ensure that there are no duplicate entries for the same withdrawal. Correct the Entry: If a duplicate entry is found, you may need to delete or reverse the previous
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