QuickBooks 2015 upgrade company file
Upgrade (convert) company file to a newer QuickBooks Desktop version
Once you convert the file to a newer version, older versions of QuickBooks will not be able to open it.
However, QuickBooks Desktop automatically backs up your data file before upgrading it, in case you need to revert to the older version. You can always restore this backup with your old version of QuickBooks Desktop if necessary. Or, if the conversion process is interrupted for any reason, you can restore the backup with your new version of QuickBooks Desktop to restart the upgrade.
