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). Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support.This guide will explain how to prove domicile when filling out Form I-864 ("Affidavit of Support"). Examples of acceptable evidence. Description. Residence in the U.S.. Lease agreement; Mortgage payments; Utility bills. 1. Fill in the parcel number of the property for which you are seeking a homestead exclusion.