Message type: E = Error
Message class:  FKKINV - Invoicing in Contract Accounts Receivable and Payable 
Message number: 335
Message text: You are changing the rules for individual charges/discounts in the past
If invoicing runs are repeated with the same dataset to be invoiced,
this can lead to different results.
The system issues an error message and will not allow you to continue with this transaction until the error is resolved.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message FKKINV335 indicates that you are attempting to change the rules for individual charges or discounts in the past, which is not allowed in the system. This error typically arises in the context of billing or invoicing processes within the SAP Convergent Charging or Contract Accounts Receivable and Payable (FI-CA) modules.
Cause: Historical Data Integrity: SAP maintains the integrity of historical data. Changing rules for charges or discounts that have already been applied to past transactions can lead to inconsistencies and inaccuracies in financial reporting. Configuration Changes: If you are trying to modify the configuration settings for charges or discounts that have already been processed, the system will prevent this to ensure that past transactions remain unchanged.
Solution: Review Changes: Ensure that you are not trying to apply changes to historical data. If you need to change rules, do so for future transactions only. Create New Rules: If you need to implement new
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