(35 ILCS 5/911) (from Ch. 120, par. 9-911)
    Sec. 911. Limitations on claims for refund.
    (a) In general. Except as otherwise provided in this Act:
        (1) A claim for refund shall be filed not later than
    
3 years after the date the return was filed (in the case of returns required under Article 7 of this Act respecting any amounts withheld as tax, not later than 3 years after the 15th day of the 4th month following the close of the calendar year in which such withholding was made), or one year after the date the tax was paid, whichever is the later; and
        (2) No credit or refund shall be allowed or made with
    
respect to the year for which the claim was filed unless such claim is filed within such period.
    (b) Federal changes.
        (1) In general. In any case where notification of an
    
alteration is required by Section 506(b), a claim for refund may be filed within 2 years after the date on which such notification was due (regardless of whether such notice was given), but the amount recoverable pursuant to a claim filed under this Section shall be limited to the amount of any overpayment resulting under this Act from recomputation of the taxpayer's net income, net loss, or Article 2 credits for the taxable year after giving effect to the item or items reflected in the alteration required to be reported.
        (2) Tentative carryback adjustments paid before
    
January 1, 1974. If, as the result of the payment before January 1, 1974 of a federal tentative carryback adjustment, a notification of an alteration is required under Section 506(b), a claim for refund may be filed at any time before January 1, 1976, but the amount recoverable pursuant to a claim filed under this Section shall be limited to the amount of any overpayment resulting under this Act from recomputation of the taxpayer's base income for the taxable year after giving effect to the federal alteration resulting from the tentative carryback adjustment irrespective of any limitation imposed in paragraph (1) of this subsection.
    (c) Extension by agreement. Where, before the expiration of the time prescribed in this section for the filing of a claim for refund, both the Department and the claimant shall have consented in writing to its filing after such time, such claim may be filed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon. In the case of a taxpayer who is a partnership, Subchapter S corporation, or trust and who enters into an agreement with the Department pursuant to this subsection on or after January 1, 2003, a claim for refund may be filed by the partners, shareholders, or beneficiaries of the taxpayer at any time prior to the expiration of the period agreed upon. Any refund allowed pursuant to the claim, however, shall be limited to the amount of any overpayment of tax due under this Act that results from recomputation of items of income, deduction, credits, or other amounts of the taxpayer that are taken into account by the partner, shareholder, or beneficiary in computing its liability under this Act.
    (d) Limit on amount of credit or refund.
        (1) Limit where claim filed within 3-year period. If
    
the claim was filed by the claimant during the 3-year period prescribed in subsection (a), the amount of the credit or refund shall not exceed the portion of the tax paid within the period, immediately preceding the filing of the claim, equal to 3 years plus the period of any extension of time for filing the return.
        (2) Limit where claim not filed within 3-year period.
    
If the claim was not filed within such 3-year period, the amount of the credit or refund shall not exceed the portion of the tax paid during the one year immediately preceding the filing of the claim.
    (e) Time return deemed filed. For purposes of this section a tax return filed before the last day prescribed by law for the filing of such return (including any extensions thereof) shall be deemed to have been filed on such last day.
    (f) No claim for refund or credit based on the taxpayer's taking a credit for estimated tax payments as provided by Section 601(b)(2) or for any amount paid by a taxpayer pursuant to Section 602(a) or for any amount of credit for tax withheld pursuant to Article 7 may be filed unless a return was filed for the tax year not more than 3 years after the due date, as provided by Section 505, of the return which was required to be filed relative to the taxable year for which the payments were made or for which the tax was withheld. The changes in this subsection (f) made by this amendatory Act of 1987 shall apply to all taxable years ending on or after December 31, 1969.
    (g) Special Period of Limitation with Respect to Net Loss Carrybacks. If the claim for refund relates to an overpayment attributable to a net loss carryback as provided by Section 207, in lieu of the 3 year period of limitation prescribed in subsection (a), the period shall be that period which ends 3 years after the time prescribed by law for filing the return (including extensions thereof) for the taxable year of the net loss which results in such carryback (or, on and after August 13, 1999, with respect to a change in the carryover of an Article 2 credit to a taxable year resulting from the carryback of a Section 207 loss incurred in a taxable year beginning on or after January 1, 2000, the period shall be that period that ends 3 years after the time prescribed by law for filing the return (including extensions of that time) for that subsequent taxable year), or the period prescribed in subsection (c) in respect of such taxable year, whichever expires later. In the case of such a claim, the amount of the refund may exceed the portion of the tax paid within the period provided in subsection (d) to the extent of the amount of the overpayment attributable to such carryback. On and after August 13, 1999, if the claim for refund relates to an overpayment attributable to the carryover of an Article 2 credit, or of a Section 207 loss, earned, incurred (in a taxable year beginning on or after January 1, 2000), or used in a year for which a notification of a change affecting federal taxable income must be filed under subsection (b) of Section 506, the claim may be filed within the period prescribed in paragraph (1) of subsection (b) in respect of the year for which the notification is required. In the case of such a claim, the amount of the refund may exceed the portion of the tax paid within the period provided in subsection (d) to the extent of the amount of the overpayment attributable to the recomputation of the taxpayer's Article 2 credits, or Section 207 loss, earned, incurred, or used in the taxable year for which the notification is given.
    (h) Claim for refund based on net loss. On and after August 23, 2002, no claim for refund shall be allowed to the extent the refund is the result of an amount of net loss incurred in any taxable year ending prior to December 31, 2002 under Section 207 of this Act that was not reported to the Department within 3 years of the due date (including extensions) of the return for the loss year on either the original return filed by the taxpayer or on amended return or to the extent that the refund is the result of an amount of net loss incurred in any taxable year under Section 207 for which no return was filed within 3 years of the due date (including extensions) of the return for the loss year.
    (i) Periods of limitation suspended while taxpayer is unable to manage financial affairs due to disability. In the case of an individual, the running of the periods specified in this Section shall be suspended during any period when that individual is financially disabled.
    For purposes of this subsection (i), an individual is financially disabled if that individual is unable to manage his or her financial affairs by reason of a medically determinable physical or mental impairment of the individual that can be expected to result in death, or which has lasted or can be expected to last for a continuous period of not less than 12 months.
    An individual shall not be treated as financially disabled during any period when that individual's spouse or any other person is authorized to act on behalf of that individual with respect to financial matters.
(Source: P.A. 97-507, eff. 8-23-11; 98-970, eff. 8-15-14.)