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.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. In this post, we'll explore examples of proof of US domicile and the documents required to establish proof of domicile. I've heard of using that in the domicile package too, if you stated your address as an actual US address. You have to have three documents with you to enter the U.S. as an immigrant: your passport, your immigrant visa, and your medical report in a sealed envelope.