Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support. 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).How Can I Prove U.S. Domicile? Examples of acceptable evidence. Description. Residence in the U.S.. Lease agreement; Mortgage payments; Utility bills. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. In this post, we'll explore examples of proof of US domicile and the documents required to establish proof of domicile. All domicile must be established at least one year immediately prior to the first day of the quarter the student is seeking residency. This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile.