Land taxes are based on legal issues and legal stuff, so they are not the same across world. You can read the legal papers of your state, convert them into a
pseudo code[
^]. That will help you (and will assist you) while writing the code for the application.
This seems like a simple Mathematical problem solving application, where you pass one or two parameters as input and the software does the calculations and give back a result. You can feel some friendly relations with
MSDN[
^], they would guide you in writing the good syntax.