No, your computer does not have to be on all the time. It must be on and connected to the Internet during the time-period you specified for backup. When the computer is turned off during backup time, or your Internet connection interrupted, the system will automatically attempt a backup the next time it is turned on and it can access the Internet. You can also select an option in the dinKum software configuration area where your computer will shut down automatically after the scheduled backup has been successfully completed.