Hey there, userdwilliamsca.
Thanks for reaching out to the Community for support. I'd be happy to provide some information.
There isn't the option to generate T5 forms in QuickBooks Online. I can see how this may be beneficial for you so I recommend leaving feedback for our developers. Comments are viewed and considered as they create new features and updates for QuickBooks.
In addition, I'll leave this post open for other Community members to share their experiences. If you have any other questions, feel free to reach back out here.