You need to print them out...sign them, attach any tax forms, that show any IL withholding (like W-2 forms) and send them in to IL tax people by paper mail. Include your payment if you owe IL some more $$, ANNNND Use a tracking method at the PO Service Counter.
NO......you cannot file them with your 2017 taxes. Every year is considered separately .
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
