You can export .qb205 files to .qbb files using the File ► Backup to QuickBooks Windows function in QuickBooks for OS X (possibly only version 2005).
Be careful when restoring older backups, as they might overwrite your existing data. Also keep in mind that it is not possible to use a newer version of the format in the previous version of the program, i.e. you cannot open .qbb file exported from .qb2005 in Quickbooks 2004 etc.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
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