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.Learn how to prove your U.S. domicile for a family visa with our stepbystep guide. Essential documents and tips to ensure visa approval. How do I handle a proof of domicile when filling Form I864? ; What is Form I-864? Can a sponsor maintain U.S. domicile while living abroad temporarily? How can a financial petitioner establish a domicile? Complete Your Family Green Card Application Today. Start. What is Proof of U.S. Domicile?