Validate EU VAT Number checkout field

Hi Christian,

The easiest way to add a checkout field that validates a VAT number is to use a plugin such as EU VAT Number https://woocommerce.com/products/eu-vat-number/ and it does have an option to prevent checkout if VAT number is not provided or incorrect https://docs.woocommerce.com/document/eu-vat-number-2/#section-2

This plugin does not offer to add the VAT field conditionally based on items added to cart though.

In order to make this happen you’d probably have to hire a developer to code this kind of functionality for you.

If you decide to pursue such functionality and find yourself in need of help with the code – I’d recommend reaching out to someone from WooCommerce.com customizations page
https://woocommerce.com/customizations/

I can also recommend the following places for more development-oriented questions:

* WooCommerce Slack Community: 

https://woocommerce.com/community-slack/

* Advanced WooCommerce group on Facebook: 

https://www.facebook.com/groups/advanced.woocommerce/

I hope this helps!