Last year, Illinois enacted a mid-year income tax rate increase. Effective July 1, 2017, Illinois increased the income tax rate for individuals, trusts and estates from 3.75 percent to 4.95 percent, and for corporations from 5.25 percent to 7 percent. The Illinois Personal Property Replacement Tax (imposed on corporations, partnerships, trusts, S corporations and public utilities at various rates) was not changed.
As we previously reported, the Illinois Income Tax Act contains a number of provisions intended to resolve questions regarding how income should be allocated between the two income tax rates applicable in 2017. 35 ILCS 5/202.5(a). The default rule is a proration based on the number of days in each period (181/184). For taxpayers choosing this method, the Department of Revenue (Department) has recommended the use of a blended tax rate to calculate tax liability. A schedule of blended rates is included in the Department’s instructions for the 2017 returns. The blended rate is 4.3549 percent for calendar year individual taxpayers and 6.1322 percent for calendar year C corporation taxpayers.