Hi there jalliston,
Thanks for reaching out about your registered charity. QuickBooks Online is a great tool able to help you keep track of tax on transactions so you know the amount to declare. I can provide some information about taxes.
In QuickBooks Online, there is the option to keep track of sales tax so you know the amount to file, but there isn't an option to physically make the filling to the government directly in QuickBooks Online, or make an Application for GST/HST Public Service Bodies' Rebate and GST Self-Government Refund. This would need to be done outside of the software itself.
If you have any other questions, feel free to reach out here.