Illinois Administrative Code
Title 86 - REVENUE
Part 100 - INCOME TAX
Subpart M - BUSINESS INCOME OF PERSONS OTHER THAN RESIDENTS
Section 100.3310 - Business Income of Persons Other Than Residents (IITA Section 304) - In General
The business income of a person other than a resident is allocated to Illinois if such person's business income is derived solely from Illinois. Note that any reference to person in this section shall refer to a person other than a resident. Every person who derives business income from Illinois and one or more other states must apportion such business income between Illinois and such other state or states in accordance with the provisions of IITA Section 304. Special apportionment rules are provided for the business income of insurance companies, financial organizations, and persons furnishing transportation services, and for alternative methods of apportionment (and allocation) where the specific statutory provisions do not fairly represent the extent of a person's business activity in Illinois. See IITA Section 304(b),(c),(d) and (e) of the Act.