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.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. They include tax returns, an employment confirmation letter and three recent check stubs or proof of income for the sponsor or petitioner. The joint sponsor must also submit Form I864 and meet the income requirements. Any nondependent siblings, parents, or adult children who reside in the sponsor's household who are not dependents, if they complete a Form I-864A. The I-864 is required in order to show that the sponsor – or joint sponsor – has adequate financial ability to support the immigrant beneficiary.