I would like it if EU tax could automatically be applied to user upgrades. This law means we should be adding tax at the rate for each country.
Shopping cart systems such as Woocommerce have identified this problem and introduced plugins to deal with it.
Hopefully somebody may come up with an addon, but I think this is very important and should be in the core of xenforo as part of the user upgrade feature.
It is of course possible instead to manually try to identify the country for each upgrade and account for the EU VAT by subtracting it from the gross, but this can be very time consuming and a clunky way of doing it.
This is currently the only workaround and until there is a more elegant solution, it would help if at least a display of the customer location in the list of active upgrades could be implemented to help identify those transactions where tax is due