Hello Massimo,
Omar is here from plugin support.
Depending on your theme (or if you’re using a plugin to control templates), you need to alter the admin-new-order template file.
The original file is located on:
woocommerce/templates/emails/admin-new-order.php
You need to add this part to it:
echo get_post_meta( $order->get_id(), ‘_billing_eu_vat_number’ , true );
If that’s controlled by your theme, you will need to add that line to:
your-theme/woocommerce/emails/admin-new-order.php.
Please let us know if you need further help, we will be happy to set this up for you, just send us FTP access to [email protected] and we’ll take care of that.
Omar