Ill. Admin. Code tit. 86 § 100.3340
In filing returns with this state, if any person departs from or modifies the manner in which income has been classified as business income or nonbusiness income in returns for prior years, such person shall disclose in the return for the current year the nature and extent of the modification. If the returns or reports filed by a person for all states to which such person reports under Article IV of the Multistate Tax Compact or the Uniform Division of Income for Tax Purposes Act are not uniform in the classification of income as business or nonbusiness income, the person shall disclose in its return to this state the nature and extent of the variance.
Ill. Admin. Code tit. 86, § 100.3340
Section repealed, new Section adopted at 6 Ill. Reg. 579, effective December 29, 1981; amended at 8 Ill. Reg. 6184, effective May 4, 1984