QuickBooks Error 6123 arises when the file permissions are faulty or conflicting while creating a backup of data files. The reason behind it is a corrupt company file, a lack of sufficient permissions, or interference from the firewall or antivirus program. It also gets initiated by network issues or external drive-related issues if the backup location cannot be accessed. It can be fixed by opening QuickBooks in administrator mode, repairing and checking the company file data, or modifying the backup location to a local folder such as the desktop.

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