Hi there mmz89-yahoo-ca,
It's important that all your transactions be entered correctly for your books to be well balanced. It's a great tool allowing you to have access to your books from any location with an internet connection. I can provide some information about the QuickBooks Online Mobile App.
The QuickBooks Online Mobile App is included with any QuickBooks Online subscription level for no extra charge other than the subscription fee for the subscription itself. You can view the subscription level and their prices by going to qbo.ca, then selecting the plans and prices section. You can download the App by going to the App Store on your mobile device and searching for QuickBooks Online.
If you have any other questions, feel free to reach out here.