The rate of interest charged on delinquent taxes is set by state law. At the commissioner’s meeting on Friday the tax rate was said to be 11% or 10%. I just got a fax from the treasurer’s department that shows the actual interest rate for each year. The current amount is considerably lower. According to Susan Quick the interest is locked in at the current rate when the taxes were due. So if someone doesn’t pay their 2008 taxes and the rate for 2008 was 11%, all of the interest on those outstanding taxes will be charged at 11%–regardless of what year the taxes are eventually paid.
Below is a chart showing what the tax rate is for each year. (pdf source)