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. Completing and signing Form I-864 makes you the sponsor.If you are filing Form I864 as the petitioning sponsor, use our How to Fill Out Affidavit of Support Form I864 guide. In this guide, we will explain who needs to complete Form I864, when to file it, and how to fill out Form I864 stepbystep. Stepbystep instructions on filling out Form I864, Affidavit of Support. This video will help you to fill out I-864 For Joint Sponsor. The purpose of the Affidavit is to assist consular officers in determining whether a visa applicant will have adequate means of financial support in the US. The joint sponsor must fill out form I-864 Affidavit of Support as well as the petitioner. 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. What do I need to show to be a Sponsor for the Affidavit of Support?