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. If you have a joint sponsor, they must also complete Form I864.If you have a joint sponsor, the joint sponsor must also complete and sign USCIS Form I-864. You, the sponsor (petitioner), and the joint sponsor must complete Form I-864. See tips for completing Form I-864. We assist our clients in preparing and filing form I-864, Affidavit of Support, on their behalf or on behalf of their family member. This video will help you to fill out I-864 For Joint Sponsor. LPRs whose sponsor signed a legally binding affidavit of support (U. In today's video we are going to be filling out form i 864 the affidavit of support form for the joint sponsor. Visa petitioner (US Citizen) will have to complete form I134.