VAT validation

In admin mode I have following settings:


EU VAT enabled  : yes
Your shop country :Belgium  

Allow VAT exemption : yes  

Assume VAT always valid  :no

Use web service: yes

Notify admin when a new VAT number is submitted :no

During registration the user must choose his country en give a VAT-number.  But as VAT number the customer can write everything!
  Why there is not VAT validation?????

I found out in the code that there is wel can be a VAT validation. How can I make validation enable?