Hi,
Looking at your screenshot, you Tax settings are wrong.
– You have set your prices to be inclusive of tax, this needs to be changed to “No, I will enter prices exclusive of tax”.
– You also have this wrong: “Display Prices During Cart and Checkout:” please change to Display Prices During Cart and Checkout: Excluding Tax.
Please change those settings. If you disabled the theme and the problem persists, it is not a theme issue. Please update the settings recommended above.
– David.