If you have a joint sponsor, they must also complete Form I864. Use this form to show they have adequate means of financial support and are not likely to rely on the US government for financial support.You, the sponsor (petitioner), and the joint sponsor must complete Form I-864. See tips for completing Form I-864. I am sponsoring the following family members immigrating at the same time or within six months of the principal immigrant named in Part 2. In today's video we are going to be filling out form i 864 the affidavit of support form for the joint sponsor. Form I864, Affidavit of Support, needs to be filed DHS if you are a U.S. citizen or LPR planning to sponsor a spouse or family member. They must also complete a Form I864A, Contract between Sponsor and Household Member. 1-864 Affidavit of Support: Asset calculations. Someone who wants to sponsor a prospective immigrant to Atlanta must first complete and sign Form I-864, often referred to as an "affidavit of support.