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. This tip sheet will help you complete Form I864, Affidavit of Support Under Section 864A of the INA. Detailed.You, the sponsor (petitioner), and the joint sponsor must complete Form I-864. See tips for completing Form I-864. An Affidavit of Support is US Immigration Form I-864. Line-by-line guidance for properly filling out USCIS's I-864 Affidavit of Support to sponsor an immigrating family member. The joint sponsor must also submit Form I864 and meet the income requirements. Attorney David M. Nguyen discusses how to complete USCIS Form I-864, Affidavit of Support. The I-864 is required in order to show that the sponsor – or joint sponsor – has adequate financial ability to support the immigrant beneficiary. If you are filing Form I864 as the petitioning sponsor, use our How to Fill Out Affidavit of Support Form I864 guide.