In Illinois, in its simplest terms, forgery can be understood as the knowing and willful falsification of signatures, documents, or objects. Under Illinois law, forgery is generally considered a Class 3 felony.A person commits forgery when, with intent to defraud, he or she knowingly: (1) makes a false document or alters any document to make it false. Free Consultation - Call (312) 902-3344 - This page covers the state legislation, punishments, examples and possible legal defenses concerning forgery. With most types of forgery, you will be charged with a Class 3 felony.