How to Fill Out an Affidavit An affidavit is a paper or written declaration filed as evidence in court by an affiant. To be acceptable, affidavits must be notarized by a notary public. You can file an unnotarized affidavit with the court if you want, but it won't be accepted as evidence. A notary public charges $20 for services performed in Washington state. An affidavit is usually used as evidence that a person has declared under oath (or affirmed) the contents of a document. For example, if a husband and wife have been married for several years and plan to divorce, she could file an affidavit with the court stating that he is mentally ill and therefore should not be forced to pay child support. The court would accept this affidavit as evidence that he is not responsible for paying child support. People sometimes use affidavits as a way of making claims without appearing in court. For example, they might send a letter to the court claiming that someone else is responsible for paying child support. If this letter is signed under oath or affirmation then it is called an "affidavit". There are two types of affidavits: statutorily authorized affidavits and factually authorized affidavits. Statutorily authorized affidavits are required for certain procedures before a marriage can be terminated (see below).