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).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. This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. These additional financial sponsors also have to submit an Affidavit of Support, proof of their income, and proof of their legal status in the United States. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. I am household member and filled form 1864A and added as a household member i was asked to provide proof of citizenship and proof of domicile.