The Assign function on the Account List has an option to do a quick backup before actioning the Assign request. This can be useful to tick as it gives some security in case you actually need to reverse the function just about to be actioned. However, if you intend to rely on it, you must ensure that no one else uses the current Database Area between the backup and the restore.

Backup

Tick the box for Quick Backup in the Assign section, before clicking the Apply button. The backup only affects the current Database Area and creates an internal copy of all the accounts section of the database regardless of any filters. The previous backup is overwritten each time an assign takes place in that Area. Multiple users doing quick backups will mean that their backups will overwrite yours

Restore

Go to the menu option Tools > Restore Quick Backup

Restore only accounts missing from live database -

Restore specific account number(s) -