Illinois Statutes Chapter 35. Revenue § 5/301. General Rule

(1) In general. Any item of income or deduction which was taken into account in the computation of base income for the taxable year by any person other than a resident and which is referred to in Section 302, 303 or 304 (relating to compensation, nonbusiness income and business income, respectively) shall be allocated to this State only to the extent provided by such section.

(2) Unspecified items. Any item of income or deduction which was taken into account in the computation of base income for the taxable year by any person other than a resident and which is not otherwise specifically allocated or apportioned pursuant to Section 302, 303 or 304 (including, without limitation, interest, dividends, items of income taken into account under the provisions of Sections 401 through 425 of the Internal Revenue Code,  1 and benefit payments received by a beneficiary of a supplemental unemployment benefit trust which is referred to in Section 501(c)(17) of the Internal Revenue Code):  2