This tip sheet will help you complete Form I864, Affidavit of Support Under Section 864A of the INA. Detailed. NOTE: As a sponsor, you must include proof of your U.S. citizenship, U.S. national status, or lawful permanent resident status.Line-by-line guidance for properly filling out USCIS's I-864 Affidavit of Support to sponsor an immigrating family member. In this guide, we will explain who needs to complete Form I864, when to file it, and how to fill out Form I864 stepbystep. The applicant must use this affidavit to support their claim of residency or being domiciled in Texas. 864 Affidavit of support How to fill out the Form 864 immigration Tips. All child support forms are categorized and linked below as downloadable files. Select the category you need to see the corresponding forms. Contact the Texas Comptroller of Public. Contact the Texas Comptroller of Public.