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.An affidavit for a signature witnessing that is in substantially the following form is sufficient under Subsection (1):. After filling out your forms, file them with the justice court where your case was filed. An affidavit is a voluntary, sworn statement made under oath, used as verification for various purposes. AFFIDAVIT. I swear that the following is true: (1) Claim Amount plus attorney's fees (If applicable).