Q. Are foreign pensions taxable in Illinois? A. Pensions received from other countries are not excluded from income for IL tax purposes and are.You must file Form IL-W-4 when Illinois. Income Tax is required to be withheld from compensation that you receive as an em- ployee. Every employer who maintains an office or transacts business in Iowa and who is required to withhold federal income tax on any compensation paid to employees. Wisconsin generally will not tax the salaries, wages, commissions, fees, etc. Employers must withhold Illinois income tax for nonresident employees who spend more than 30 working days in Illinois starting in 2020. APPLICATION: Please complete and submit two copies of form BCA 13.15 to apply for an Authority to Transact Business in Illinois. International staff who is not a Permanent Resident. The legislation created a uniform 30day threshold for a nonresident to be subject to Illinois income tax.