If your calculator has a TAX EXCH or TAX RATE label above a key, it supports this function.
If your calculator is a basic scientific model without dedicated tax buttons, you will need to calculate tax manually using the multiplication and addition keys. how to set tax rate in casio calculator
Write your current tax rate on a sticker and place it on the back of your calculator. That way, anyone using it can quickly verify or reset the rate without guessing. If your calculator has a TAX EXCH or