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. I am sponsoring the following family members immigrating at the same time or within six months of the principal immigrant named in Part 3.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 I-864, Affidavit of Support is a required piece of paperwork in all family-based immigration cases, including those based on marriage. The visa petitioner is required to sign the Form I-864. The person who signs the Affidavit of Support is also called the "sponsor. The Affidavit of support is filed to establish willingness and ability to financially support your immigrant spouse or family member. Do not need to complete Form. 864A because he or she is the intending immigrant and has no accompanying dependents.