Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support. How do I handle a proof of domicile when filling Form I864?To complete Form I-864, the petitioner must meet certain requirements. This article discusses the difference between domicile and residence in this context, and how sponsors can establish and prove their domicile for Form I-864. 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). The IRS provides this residency certification on Form 6166, a letter of U.S. residency certification. Both documents must show your first and last names and the same address that is listed on the driver license or identification card application. A driver's license, or some sort of bill, like a utility bill, that shows your name and address. 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.