Hi,
That's not a problem. In the product, you don't select the tax rate that will apply to the product. You select the tax category.
And in the menu System>Taxes, you can create several tax rules in order to link your tax rates with the tax categories.
That way, you can have several tax rules:
- one for the tax rate 21% and the tax category of your products and the user group of your normal and public customers
- one for the tax rate 26.2% and the tax category of your products and the user group of your extra charge customers
Also, you can create a tax zone via the menu System>Zones with all the states and countries for which your tax rules should apply and select it in your tax rules. That way, the tax rules won't apply for customers outside these zones.