35 ILCS 5/703
Every employer required to deduct and withhold tax under this Act from compensation of an employee, or who would have been required so to deduct and withhold tax if the employee's withholding exemption were not in excess of the basic amount in Section 204(b), shall furnish in duplicate to each such employee in respect of the compensation paid by such employer to such employee during the calendar year on or before January 31 of the succeeding year, or, if his employment is terminated before the close of such calendar year, on the date on which the last payment of compensation is made, a written statement in such form as the Department may by regulation prescribe showing the amount of compensation paid by the employer to the employee, the amount deducted and withheld as tax, and such other information as the Department shall prescribe. A copy of such statement shall be filed by the employee with his return for his taxable year to which it relates (as determined under Section 601(b)(1)).
35 ILCS 5/703