2020 IL-1120-ST Instructions - Illinois

Reminder: Taxpayers making an extension payment, an estimated payment, a voluntary prepayment of their tax liabilities, or a return payment should pay electronically using MyTax.Illiois.gov or mail Form IL-1120-ST-V, Payment Voucher for Small Business Corporation Replacement Tax. Use for tax year ending on or before December 31, 2021. ................
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