70 ILCS 504/40
The creation of the Authority is in all respects for the benefit of the people of Illinois and for the improvement of their health, safety, welfare, comfort, and security, and its purposes are public purposes. In consideration thereof, the notes and bonds of the Authority issued pursuant to this Act and the income from these notes and bonds may be free from all taxation by the State or its political subdivisions, except for estate, transfer, and inheritance taxes. The exemption from taxation provided by the preceding sentence shall apply to the income on any notes or bonds of the Authority only if the Authority in its sole judgment determines that the exemption enhances the marketability of the bonds or notes or reduces the interest rates that would otherwise be borne by the bonds or notes. For purposes of Section 250 of the Illinois Income Tax Act, the exemption of the Authority shall terminate after all of the bonds have been paid. The amount of such income that shall be added and then subtracted on the Illinois income tax return of a taxpayer, subject to Section 203 of the Illinois Income Tax Act, from federal adjusted gross income or federal taxable income in computing Illinois base income shall be the interest net of any bond premium amortization.
70 ILCS 504/40