Not quite sure I understand but I will try to explain how taxes and square works. From your dashboard you go to taxes and create the taxes you need. Just as an example let’s use sales tax. Here in California sales tax applies to every thing except food items. So once you create the tax you have the option to go thru your item list and select the items or categories that the tax will apply to. At that point it should be automatically applied at time of sale. That will also show up as an option in each item so at time of sale you should be able to click on each item in your cart and scroll down to see the option to toggle tax on or off for that item for that sale only