The default from our system is “Rest of the World”, this means that from wherever your customers come from, the tax rate is flat according to the percentage you set. If you only serve for domestic customers or of certain country, then it’s recommended that you set tax percentage based on that specific country’s tax rate.
Click ‘Add New Destination’ button on top right of the page, then tick on the country you want to set from the provided list; it will get automatically added into the table.
Click ‘Edit’ next to it and set the percentage of that country tax rate as you know.
If all your products’ prices are already included with tax, then you can tick the box on top of page and your customers won’t be charged with extra tax when checkout (what does this mean?). You can also set tax to shipping rate you handle (learn more here).