If the GC system does not accept your EU VAT one of the following cases is true

• The entered VAT is not a valid EU VAT registered with VIES (VAT Information Exchange System) 
• The entered VAT does not match the selected billing country
• The entered VAT does not match the selected legal form
• The entered VAT is not a VAT but a tax number. In this case please add it to the correct input field "Tax number"