(35 ILCS 5/601) (from Ch. 120, par. 6-601)

Sec. 601. Payment on due date of return.

(a) In general. Every taxpayer required to file a return under this Act shall, without assessment, notice or demand, pay any tax due thereon to the Department, at the place fixed for filing, on or before the date fixed for filing such return (determined without regard to any extension of time for filing the return) pursuant to regulations prescribed by the Department. If, however, the due date for payment of a taxpayer's federal income tax liability for a tax year (as provided in the Internal Revenue Code or by Treasury regulation, or as extended by the Internal Revenue Service) is later than the date fixed for filing the taxpayer's Illinois income tax return for that tax year, the Department may, by rule, prescribe a due date for payment that is not later than the due date for payment of the taxpayer's federal income tax liability. For purposes of the Illinois Administrative Procedure Act, the adoption of rules to prescribe a later due date for payment shall be deemed an emergency and necessary for the public interest, safety, and welfare.

(b) Amount payable. In making payment as provided in this section there shall remain payable only the balance of such tax remaining due after giving effect to the following:

(1) Withheld tax. Any amount withheld during any calendar year pursuant to Article 7 from compensation paid to a taxpayer shall be deemed to have been paid on account of any tax imposed by subsections 201(a) and (b) of this Act on such taxpayer for his taxable year beginning in such calendar year. If more than one taxable year begins in a calendar year, such amount shall be deemed to have been paid on account of such tax for the last taxable year so beginning.

(2) Estimated and tentative tax payments. Any amount of estimated tax paid by a taxpayer pursuant to Article 8 for a taxable year shall be deemed to have been paid on account of the tax imposed by this Act for such taxable year.

(3) Foreign tax. The aggregate amount of tax which is imposed upon or measured by income and which is paid by a resident for a taxable year to another state or states on income which is also subject to the tax imposed by subsections 201(a) and (b) of this Act shall be credited against the tax imposed by subsections 201(a) and (b) otherwise due under this Act for such taxable year. For taxable years ending prior to December 31, 2009, the aggregate credit provided under this paragraph shall not exceed that amount which bears the same ratio to the tax imposed by subsections 201(a) and (b) otherwise due under this Act as the amount of the taxpayer's base income subject to tax both by such other state or states and by this State bears to his total base income subject to tax by this State for the taxable year. For taxable years ending on or after December 31, 2009, the credit provided under this paragraph for tax paid to other states shall not exceed that amount which bears the same ratio to the tax imposed by subsections 201(a) and (b) otherwise due under this Act as the amount of the taxpayer's base income that would be allocated or apportioned to other states if all other states had adopted the provisions in Article 3 of this Act bears to the taxpayer's total base income subject to tax by this State for the taxable year. This subsection is exempt from the 30-day threshold set forth in subparagraph (iii) of paragraph (B) of item (2) of subsection (a) of Section 304. The credit provided by this paragraph shall not be allowed if any creditable tax was deducted in determining base income for the taxable year. Any person claiming such credit shall attach a statement in support thereof and shall notify the Director of any refund or reductions in the amount of tax claimed as a credit hereunder all in such manner and at such time as the Department shall by regulations prescribe.

(4) Accumulation and capital gain distributions. If the net income of a taxpayer includes amounts included in his base income by reason of Section 667 of the Internal Revenue Code (relating to accumulation and capital gain distributions by a trust, respectively), the tax imposed on such taxpayer by this Act shall be credited with his pro rata portion of the taxes imposed by this Act on such trust for preceding taxable years which would not have been payable for such preceding years if the trust had in fact made distributions to its beneficiaries at the times and in the amounts specified in Sections 666 and 669 of the Internal Revenue Code. The credit provided by this paragraph shall not reduce the tax otherwise due from the taxpayer to an amount less than that which would be due if the amounts included by reason of Section 667 of the Internal Revenue Code were excluded from his or her base income.

(c) Cross reference. For application against tax due of overpayments of tax for a prior year, see Section 909.

(Source: P.A. 101-585, eff. 8-26-19.)