If you want to legally change your name, you must fill out and file name change forms with the court. Then, you will have a hearing in front of a judge.Any person who has been a resident of the State of Illinois for six (6) months and is a resident of Cook County may petition the court for a change of name. File your forms in the Circuit Clerk's office. Your Request for Name Change (Adult) has to be notarized prior to filing. What forms do I need to fill out to change my name? O Request for Name Change: gives the court the information needed to decide if you can change your name. To change your name in Illinois, you'll need to complete at least three easy forms. An attorney can help you prepare these documents. Fill out Social Security form SS-5, print it and take the form to your local Social Security Office.