Affidavit of Support, Form I-864. A document promising that the person who completes it will support an applicant financially in the U.S. Family and certain employment immigration cases require the I-864 Affidavit of Support, which is legally binding.All other cases use the I-134 Affidavit of Support. Go to our I-864 information to learn more. Found on https://www.encyclo.co.uk/local/22451