This form is filed with the Court after the service is done. This form is called an Affidavit of Service.An affidavit of service, also sometimes called a proof of service affidavit, is a type of affidavit that relates to legal documents that are filed with a court. The Affidavit of Service is a statement made under oath that the other party was served. 6. What happens after the other party is served? An affidavit of service is a legal document. Proof of service is a document that functions like a legal "receipt" confirming the delivery of documents from one party to another in a legal matter. An affidavit of service, or proof of service, is a sworn statement that a designated process server has served legal documents to a party in a lawsuit.