Thank you for your quick response!
I tried it, but it doesn’t work.
1. The webshop is set to 27% VAT. 27% is added to the net price of the products.
2. If the Hungarian tax number is valid, the site should work with 0% VAT. This works. The net price must be shown to the customer.
3. If the Hungarian tax number is invalid, then the Romanian 19% VAT must be used. Net price plus 19%.