Customer Address Attributes
Custom address attributes can be set up if you need to provide additional information, such as an optional email address, Skype account, alternate phone number, building, or county. The custom attribute can then be incorporated into the address template that is used to produce sales documents.
The customer VAT ID value is stored in the vat_id customer address attribute. The default label of this attribute is VAT number. The VAT number field is always present in all shipping and billing customer addresses when viewed from the Admin, but is not required.
The process for creating a custom address attribute is almost the same as creating a customer attribute. Customer address attributes can be used in the following forms: