An affidavit is a written declaration under oath, made without notice to the adverse party. Please note – in all events, both an Affidavit and unsworn Declaration must be based on the personal knowledge of the person signing.An affidavit is a written statement. A person, known as the affiant, swears under oath to the statement's truthfulness. Sworn statements are often (but not always) called affidavits. A sworn statement, also known as an affidavit or sworn declaration, is a document that presents facts relevant to a legal proceeding. A sworn statement is a construction document that lists the contractors and suppliers that provide material or labor to a construction project. This guide is for anyone who wants to file with the. Affidavits, or notarized sworn statements, are used to swear that any written statement or fact is legally valid. An affidavit is a sworn or affirmed statement made before a notary public or any public official who has the authority to administer oaths.