Generally, a plaintiff in a court case files an affidavit of service by filling out a written form provided by the court that details how court papers were delivered to the other party, having the person who carried out the service sign the form in front of a notary, and filing the form with the court, explains the New York State Unified Court System. Each court system has its own rules, so the procedure for filing the affidavit can change.
An affidavit of service, also called a proof of service or certificate of service, is a sworn legal statement to the court, in writing, that legal papers were delivered to the other party to a court case, thereby providing adequate notice under the court rules that the party must answer or appear to resolve a complaint or an aspect of a case. The format of the affidavit can differ, depending on the court rules and the type of case, but typically, the document should detail what papers were delivered, who delivered the papers, where and how the papers were delivered, the date and time of delivery, and a description of the person who received the document, explains the New York State Unified Court System.
Typically, courts provide an affidavit form that a party to a case can simply fill out and have notarized. Most courts provide different forms depending upon whether service was done in person, by mail or by publication, explains LawHelp.org.