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. In order to fill out an affidavit of support as a sponsor, you must be a U.S. citizen or green card holder.The "Affidavit of Support" is a signed document to accept financial responsibility for a family member who is seeking a green card. This form is required in most familybased green card applications, including CR1 and IR1 spouse visas and some employmentbased green card applications. The person filling out and signing Form I864 is usually the sponsor who filed the visa petition for the intending immigrant. Affidavit of Support: Your sponsor must complete an Affidavit of Support Form. Submit a completed Affidavit of Support form. Sponsors who are US citizens and permanent residents should complete the USCIS Form I-134 Affidavit of Support. What are the steps to complete an Affidavit of Support? Immigration assistance providers may offer the following services:.