After the Affidavit of Service is done, it must be filed with the Court. An affidavit is a sworn statement of fact that can be used in a variety of legal proceedings, from bankruptcy cases to family and civil litigation matters.In a nutshell, an affidavit is a sworn statement that is documented in writing. The undersigned affiant,. An affidavit is a legal document that takes the place of oral testimony in legal proceedings.