Illinois Statutes Chapter 740. Civil Liabilities § 170/2. When demand may be made on employer

(1) There has been a default of more than 40 days in payment of the indebtedness secured by the assignment and the default has continued to the date of the demand;

(2) The demand contains a correct statement as to the amount the wage-earner is in default and the original or a copy of the assignment is exhibited to the employer; and

(3) Not less than 20 days before serving the demand, notice required under Section 2.2 has been served upon the employee, and an advice copy sent to the employer, by 2 methods: (i) first class mail; and (ii) registered or certified mail.