Message type: E = Error
Message class:  AUR - Unbilled Revenue Reporting and Mass Simulation 
Message number: 013
Message text: This function is only possible for billed simulation indexes
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The SAP error message AUR013, which states "This function is only possible for billed simulation indexes," typically occurs in the context of billing or invoicing processes within the SAP system, particularly when dealing with simulation indexes in the SAP Convergent Invoicing (CI) module.
Cause: The error arises when a user attempts to perform an operation that is only applicable to billed simulation indexes, but the current index being referenced is not a billed simulation index. This can happen in scenarios such as: Trying to execute a billing-related function (like billing document creation or adjustments) on an index that has not been finalized or billed. Attempting to access or manipulate data that is not in the correct state for the operation being performed.
Solution: To resolve the AUR013 error, consider the following steps: Check Index Status: Verify the status of the simulation index you are working with. Ensure that it is indeed a billed simulation index. You can
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