(35 ILCS 5/502) (from Ch. 120, par. 5-502)

Sec. 502. Returns and notices.

(a) In general. A return with respect to the taxes imposed by this Act shall be made by every person for any taxable year:

(1) for which such person is liable for a tax imposed by this Act, or

(2) in the case of a resident or in the case of a corporation which is qualified to do business in this State, for which such person is required to make a federal income tax return, regardless of whether such person is liable for a tax imposed by this Act. However, this paragraph shall not require a resident to make a return if such person has an Illinois base income of the basic amount in Section 204(b) or less and is either claimed as a dependent on another person's tax return under the Internal Revenue Code, or is claimed as a dependent on another person's tax return under this Act.

Notwithstanding the provisions of paragraph (1), a nonresident (other than, for taxable years ending on or after December 31, 2011, a nonresident required to withhold tax under Section 709.5) whose Illinois income tax liability under subsections (a), (b), (c), and (d) of Section 201 of this Act is paid in full after taking into account the credits allowed under subsection (f) of this Section or allowed under Section 709.5 of this Act shall not be required to file a return under this subsection (a).

(b) Fiduciaries and receivers.

(1) Decedents. If an individual is deceased, any return or notice required of such individual under this Act shall be made by his executor, administrator, or other person charged with the property of such decedent.

(2) Individuals under a disability. If an individual is unable to make a return or notice required under this Act, the return or notice required of such individual shall be made by his duly authorized agent, guardian, fiduciary or other person charged with the care of the person or property of such individual.

(3) Estates and trusts. Returns or notices required of an estate or a trust shall be made by the fiduciary thereof.

(4) Receivers, trustees and assignees for corporations. In a case where a receiver, trustee in bankruptcy, or assignee, by order of a court of competent jurisdiction, by operation of law, or otherwise, has possession of or holds title to all or substantially all the property or business of a corporation, whether or not such property or business is being operated, such receiver, trustee, or assignee shall make the returns and notices required of such corporation in the same manner and form as corporations are required to make such returns and notices.

(c) Joint returns by husband and wife.

(1) Except as provided in paragraph (3):

(A) if a husband and wife file a joint federal income tax return for a taxable year ending before December 31, 2009, they shall file a joint return under this Act for such taxable year and their liabilities shall be joint and several;

(B) if a husband and wife file a joint federal income tax return for a taxable year ending on or after December 31, 2009, they may elect to file separate returns under this Act for such taxable year. The election under this paragraph must be made on or before the due date (including extensions) of the return and, once made, shall be irrevocable. If no election is timely made under this paragraph for a taxable year:

(i) the couple must file a joint return under this Act for such taxable year,

(ii) their liabilities shall be joint and several, and

(iii) any overpayment for that taxable year may be withheld under Section 909 of this Act or under Section 2505-275 of the Civil Administrative Code of Illinois and applied against a debt of either spouse without regard to the amount of the overpayment attributable to the other spouse; and

(C) if the federal income tax liability of either spouse is determined on a separate federal income tax return, they shall file separate returns under this Act.

(2) If neither spouse is required to file a federal income tax return and either or both are required to file a return under this Act, they may elect to file separate or joint returns and pursuant to such election their liabilities shall be separate or joint and several.

(3) If either husband or wife is a resident and the other is a nonresident, they shall file separate returns in this State on such forms as may be required by the Department in which event their tax liabilities shall be separate; but if they file a joint federal income tax return for a taxable year, they may elect to determine their joint net income and file a joint return for that taxable year under the provisions of paragraph (1) of this subsection as if both were residents and in such case, their liabilities shall be joint and several.

(4) Innocent spouses.

(A) However, for tax liabilities arising and paid prior to August 13, 1999, an innocent spouse shall be relieved of liability for tax (including interest and penalties) for any taxable year for which a joint return has been made, upon submission of proof that the Internal Revenue Service has made a determination under Section 6013(e) of the Internal Revenue Code, for the same taxable year, which determination relieved the spouse from liability for federal income taxes. If there is no federal income tax liability at issue for the same taxable year, the Department shall rely on the provisions of Section 6013(e) to determine whether the person requesting innocent spouse abatement of tax, penalty, and interest is entitled to that relief.

(B) For tax liabilities arising on and after August 13, 1999 or which arose prior to that date, but remain unpaid as of that date, if an individual who filed a joint return for any taxable year has made an election under this paragraph, the individual's liability for any tax shown on the joint return shall not exceed the individual's separate return amount and the individual's liability for any deficiency assessed for that taxable year shall not exceed the portion of the deficiency properly allocable to the individual. For purposes of this paragraph:

(i) An election properly made pursuant to Section 6015 of the Internal Revenue Code shall constitute an election under this paragraph, provided that the election shall not be effective until the individual has notified the Department of the election in the form and manner prescribed by the Department.

(ii) If no election has been made under Section 6015, the individual may make an election under this paragraph in the form and manner prescribed by the Department, provided that no election may be made if the Department finds that assets were transferred between individuals filing a joint return as part of a scheme by such individuals to avoid payment of Illinois income tax and the election shall not eliminate the individual's liability for any portion of a deficiency attributable to an error on the return of which the individual had actual knowledge as of the date of filing.

(iii) In determining the separate return amount or portion of any deficiency attributable to an individual, the Department shall follow the provisions in subsections (c) and (d) of Section 6015 of the Internal Revenue Code.

(iv) In determining the validity of an individual's election under subparagraph (ii) and in determining an electing individual's separate return amount or portion of any deficiency under subparagraph (iii), any determination made by the Secretary of the Treasury, by the United States Tax Court on petition for review of a determination by the Secretary of the Treasury, or on appeal from the United States Tax Court under Section 6015 of the Internal Revenue Code regarding criteria for eligibility or under subsection (d) of Section 6015 of the Internal Revenue Code regarding the allocation of any item of income, deduction, payment, or credit between an individual making the federal election and that individual's spouse shall be conclusively presumed to be correct. With respect to any item that is not the subject of a determination by the Secretary of the Treasury or the federal courts, in any proceeding involving this subsection, the individual making the election shall have the burden of proof with respect to any item except that the Department shall have the burden of proof with respect to items in subdivision (ii).

(v) Any election made by an individual under this subsection shall apply to all years for which that individual and the spouse named in the election have filed a joint return.

(vi) After receiving a notice that the federal election has been made or after receiving an election under subdivision (ii), the Department shall take no collection action against the electing individual for any liability arising from a joint return covered by the election until the Department has notified the electing individual in writing that the election is invalid or of the portion of the liability the Department has allocated to the electing individual. Within 60 days (150 days if the individual is outside the United States) after the issuance of such notification, the individual may file a written protest of the denial of the election or of the Department's determination of the liability allocated to him or her and shall be granted a hearing within the Department under the provisions of Section 908. If a protest is filed, the Department shall take no collection action against the electing individual until the decision regarding the protest has become final under subsection (d) of Section 908 or, if administrative review of the Department's decision is requested under Section 1201, until the decision of the court becomes final.

(d) Partnerships. Every partnership having any base income allocable to this State in accordance with section 305(c) shall retain information concerning all items of income, gain, loss and deduction; the names and addresses of all of the partners, or names and addresses of members of a limited liability company, or other persons who would be entitled to share in the base income of the partnership if distributed; the amount of the distributive share of each; and such other pertinent information as the Department may by forms or regulations prescribe. The partnership shall make that information available to the Department when requested by the Department.

(e) For taxable years ending on or after December 31, 1985, and before December 31, 1993, taxpayers that are corporations (other than Subchapter S corporations) having the same taxable year and that are members of the same unitary business group may elect to be treated as one taxpayer for purposes of any original return, amended return which includes the same taxpayers of the unitary group which joined in the election to file the original return, extension, claim for refund, assessment, collection and payment and determination of the group's tax liability under this Act. This subsection (e) does not permit the election to be made for some, but not all, of the purposes enumerated above. For taxable years ending on or after December 31, 1987, corporate members (other than Subchapter S corporations) of the same unitary business group making this subsection (e) election are not required to have the same taxable year.

For taxable years ending on or after December 31, 1993, taxpayers that are corporations (other than Subchapter S corporations) and that are members of the same unitary business group shall be treated as one taxpayer for purposes of any original return, amended return which includes the same taxpayers of the unitary group which joined in filing the original return, extension, claim for refund, assessment, collection and payment and determination of the group's tax liability under this Act.

(f) For taxable years ending prior to December 31, 2014, the Department may promulgate regulations to permit nonresident individual partners of the same partnership, nonresident Subchapter S corporation shareholders of the same Subchapter S corporation, and nonresident individuals transacting an insurance business in Illinois under a Lloyds plan of operation, and nonresident individual members of the same limited liability company that is treated as a partnership under Section 1501 (a)(16) of this Act, to file composite individual income tax returns reflecting the composite income of such individuals allocable to Illinois and to make composite individual income tax payments. For taxable years ending prior to December 31, 2014, the Department may by regulation also permit such composite returns to include the income tax owed by Illinois residents attributable to their income from partnerships, Subchapter S corporations, insurance businesses organized under a Lloyds plan of operation, or limited liability companies that are treated as partnership under Section 1501(a)(16) of this Act, in which case such Illinois residents will be permitted to claim credits on their individual returns for their shares of the composite tax payments. This paragraph of subsection (f) applies to taxable years ending on or after December 31, 1987 and ending prior to December 31, 2014.

For taxable years ending on or after December 31, 1999, the Department may, by regulation, permit any persons transacting an insurance business organized under a Lloyds plan of operation to file composite returns reflecting the income of such persons allocable to Illinois and the tax rates applicable to such persons under Section 201 and to make composite tax payments and shall, by regulation, also provide that the income and apportionment factors attributable to the transaction of an insurance business organized under a Lloyds plan of operation by any person joining in the filing of a composite return shall, for purposes of allocating and apportioning income under Article 3 of this Act and computing net income under Section 202 of this Act, be excluded from any other income and apportionment factors of that person or of any unitary business group, as defined in subdivision (a)(27) of Section 1501, to which that person may belong.

For taxable years ending on or after December 31, 2008, every nonresident shall be allowed a credit against his or her liability under subsections (a) and (b) of Section 201 for any amount of tax reported on a composite return and paid on his or her behalf under this subsection (f). Residents (other than persons transacting an insurance business organized under a Lloyds plan of operation) may claim a credit for taxes reported on a composite return and paid on their behalf under this subsection (f) only as permitted by the Department by rule.

(f-5) For taxable years ending on or after December 31, 2008, the Department may adopt rules to provide that, when a partnership or Subchapter S corporation has made an error in determining the amount of any item of income, deduction, addition, subtraction, or credit required to be reported on its return that affects the liability imposed under this Act on a partner or shareholder, the partnership or Subchapter S corporation may report the changes in liabilities of its partners or shareholders and claim a refund of the resulting overpayments, or pay the resulting underpayments, on behalf of its partners and shareholders.

(g) The Department may adopt rules to authorize the electronic filing of any return required to be filed under this Section.

(Source: P.A. 101-8, see Section 99 for effective date; 102-558, eff. 8-20-21.)