If you enter an amount on Form IL-1040, Line 25, attach a copy of your. Schedule IL-WIT and all your Forms W-2 and 1099 showing Illinois income and withholding.The compensation is not exempt from U.S. tax if the contractor is a U.S. resident. Who is require to withhold? • Withholding Agent. Treated just like a US citizen is, tax wise. Q. Are foreign pensions taxable in Illinois? A. Pensions received from other countries are not excluded from income for IL tax purposes and are. APPLICATION: Please complete and submit two copies of form BCA 13.15 to apply for an Authority to Transact Business in Illinois. The U.S. maintains tax treaties with over 60 different countries.