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. The Form I-864 asks for the financial sponsor's household size.If you have a joint sponsor, they must also complete Form I864. To show this, you will need the last three years of taxes and proof that you are currently employed. You, the sponsor (petitioner), and the joint sponsor must complete Form I-864. See tips for completing Form I-864. Learn what's required from a joint sponsor in connection with an affidavit of support when navigating a family green card application. You should file form I-864A with US Citizenship and Immigration Services if you are a household member who pledges to help support a sponsored immigrant. If you are assisting the joint sponsor in completing the I864, that probably means that you have agreed to represent that person. Most family-based filings require an I-864 when sponsoring an immigrant spouse, child, sibling, or parent.