An affidavit is a document which is between the petitioner and the immigrant visa applicant. An affidavit of support is a document that immigration sponsors must submit in order to take financial responsibility for an immigrant.See also Affidavit of Support. An affidavit is a written statement made under oath that is typically used in legal proceedings. Learn their purpose, when to use, and how to write. You must be the owner of the business in order to complete this form. 2. Locate one form of your identification that is on the list. 3. Affidavits are usually used to provide a sworn statement of facts to the Courts or any other government agencies. Affidavit). IMPORTANT INFORMATION ABOUT THIS DOCUMENT. WARNING TO BOTH PARTIES: This Affidavit is an important document.