i am developing a new payment module under magento.Everything going through well as usual.However, this new payment module require a cutomer tax id. by default,magento didn’t show this field for customer.To make it available for all customer,log into magento backend, goto
System > Configuration > Customers > Customer Configuration > Create New Account Options [tab]
change the config of “Show VAT Number on Frontend” to “yes”.
so how to get the new added filed — customer vat number/taxt id.you need to get billing or shipping model first.the code below as an example.
$billing = $this->getOrder()->getBillingAddress();