On Form I864, petitioners must prove that they have the ability to financially support the visa applicant(s) if necessary. 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 explain how to prove domicile when filling out Form I-864 ("Affidavit of Support"). Consular processing support without the high price tag. 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. The driver will be required to show proof of legal presence and domicile.