Illinois - Lower interest rate for first year

From the Illinois Department of Revenue Informational Bulleten FY 2004-17, dated December 2003 and subtitled "Uniform Penalty and Interest Changes" (http://www.revenue.state.il.us/publications/bulletins/2004/Fy200417.pdf):

"For interest accruing on or after January 1, 2004, the rate of interest payable on overpayments and underpayments is the 'short term federal rate' for the first year that the overpayment or underpayment accrues interest.  This rate is established by the IRS and is 3 percent less than the 'underpayment rate.'  After one year, interest will accrue on any remaining balance at the 'underpayment rate,' established under the Internal Revenue Code (IRC).

"If you have an underpayment or overpayment that is accruing interest before January 1, 2004, and the first year of interest accrual is not complete when January 1, 2004 passes, the interest rate will change to the 'short-term federal rate' for the remainder of that first year."

Note: As of January 1, 2014, the use of the short term interest rate was eliminated (https://web.archive.org/web/20141015013116/http://tax.illinois.gov/individuals/interestrate.htm).