If you don't know what VAT (Value Added Tax) is, then believe me, you are not VAT-registered and therefore have no EU VAT number. It has nothing to do with United States, it's for EU member countries in this case. You are asked for it because the payment processor used by amember.com is apparently an EU company. Just don't enter anything in the EU VAT field, but you will have to pay it on top of the product price so be prepared for it. Tomas