How does S2Member know which country the potential purchaser is located?
Am I required to create a custom registration field of "country" in order to "tell" S2member to apply the tax?
The question is true for all the tax calculation options like zip, state, province .etc.
If I am required to create these custom fields then it should be mentioned in the documentation (maybe even add a check system to make sure the required fields exist and if not show a warning)

Please let me know,
Kalman