In this post, we'll explore examples of proof of US domicile and the documents required to establish proof of domicile. If you want to sponsor someone for a family-based green card, you need to provide proof of a U.S. domicile in your Affidavit of Support (Form I-864).This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. How Can I Prove U.S. Domicile? Examples of acceptable evidence. Description. Residence in the U.S.. Lease agreement; Mortgage payments; Utility bills.