Illinois Statutes Chapter 35. Revenue § 5/602. Tentative Payments

(a) In general. Pursuant to Section 505, the Department may promulgate regulations to provide automatic extensions of the time for filing a return. In connection with any other extension provided under Section 505 of the time for filing a return, the taxpayer shall file a tentative tax return and pay, on or before the date prescribed by law for the filing of such return (determined without regard to any extensions of time for such filing), the amount properly estimated as his tax for the taxable year.

(b) Interest and Penalty. Interest and penalty on any amount of tax due and unpaid for the period of any extension shall be payable as provided by the Uniform Penalty and Interest Act.  1 However, if the taxpayer is a member, or, in the case of a joint return, the spouse of a member, of the United States Armed Forces serving in a combat zone and subject to a filing extension in accordance with a proclamation by the President of the United States pursuant to Section 7508 of the Internal Revenue Code,  2 no interest or penalty shall be applicable for the taxable year ending on and after December 31, 1990.