use different VAT rates in Product Add-ons
use different VAT rates in Product Add-ons, so you can combine a product of 21% VAT with an Product Add-on of 9% VAT
I sell classes, and offer rentals of gear. Classes are not taxable, but rentals are. I want to be able to not tax the product, but tax the rentals as an add on so customers don't have to click around to a different page to add rental gear.