Message type: E = Error
Message class:  USMDZ3 - Nachrichtenklasse zum UI des User-Interfaces 
Message number: 287
Message text: &1 &2 Account cannot be created; secondary cost element &3 exists
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The SAP error message USMDZ3287 indicates that there is an issue with creating a primary cost element because a secondary cost element already exists for the same account. This typically occurs in the context of managing cost elements in SAP's Controlling (CO) module.
Cause: The error arises when you attempt to create a primary cost element (which is used for direct posting of costs) for an account that already has a secondary cost element defined. In SAP, secondary cost elements are used for internal cost allocations and do not allow the creation of a primary cost element for the same account.
Solution: To resolve this error, you can take the following steps: Check Existing Cost Elements: Use transaction code KA03 (Display Cost Element) to check if a secondary cost element already exists for the account in question. If it does, you will need to decide whether to use the existing secondary cost element or to delete
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