On Form I864, petitioners must prove that they have the ability to financially support the visa applicant(s) if necessary. My husband and I recently submitted the document to the NVC.His father is our joint sponsor to meet the requirements for the income. How Can I Prove U.S. Domicile? Please submit proof of domicile. 864 Affidavit of support How to fill out the Form 864 immigration Tips. This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile.