How can I set up taxes correctly for rate plans and fees in the tax structure?

In the current tax structure, You can select a rate plan when creating a tax. If no rate plan is selected, the tax will not be applied to any fees associated with bookings under that rate plan.
On the Create Tax page, if you want to apply tax to a specific fee, you need to select the corresponding add-on type category of that fee from the Tax Item dropdown.
Please note that the Tax page is located under the Finance section in the main menu, not under Settings.