Message type: E = Error
Message class:  FKKID_MSG - Messages for FI-CA Loc. Cross-Country 
Message number: 108
Message text: Posting date &1 is not possible (BUKRS &2) - possible date: &3
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The SAP error message FKKID_MSG108 indicates that there is an issue with the posting date in a financial transaction. The message typically states that the specified posting date is not valid for the company code (BUKRS) in question, and it provides a possible date that can be used instead.
Cause: Closed Periods: The posting date falls within a financial period that has already been closed. In SAP, once a financial period is closed, no further postings can be made to that period. Date Restrictions: There may be specific date restrictions set up in the configuration of the company code that prevent postings on certain dates. Fiscal Year Variant: The fiscal year variant settings may restrict postings to certain periods or dates. Authorization Issues: The user may not have the necessary authorizations to post in the specified period.
Solution: Check Period Closing: Verify if the financial period for the posting date is closed. You can do this by
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