When you register a .US domain, you must certify that you are a resident or have a business within the United States. In addition, you must select a Nexus category to indicate the purpose of the domain.
In your shopping cart, beside the .US domain that you want to purchase, you will see a link called EDIT NEXUS INFO. When you click this link, the Nexus Information page appears. Use the drop-down lists to choose the appropriate information. You can enter the Nexus information while the domain is still in your shopping cart or when you check out.