If you have an EU VAT number then you will not need to pay VAT.
The VAT number is validated each time you checkout and the number is automatically checked against the EU website http://ec.europa.eu/taxation_customs/vies/
When you enter your number into the Just a Soap website do not put the country code - just enter the number.
If you add the country code as well then this is what is passed over for checking and it will fail.
So only enter the number. Any problems do get in touch with us.