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If approval is enabled and configured as "Mandatory", there will be a message when a report contains work logs without approval and the report was created with "Prepare charghing work logs" checked:
The button "Accounting - Charge Work Logs" is not usable. It won't be possible to charge the work logs and create the account. You need to get approval, or you can exclude work logs without approval from the report (see Charge Work Logs - Create Invoice).