New Construction: Why did my builder send me a tax bill (i.e. an instant assessment)?

Both seller and buyer owe property taxes for the period of time they own the property. 35 ILCS 200/9‑180 explains that owners of property shall be liable, on a proportionate basis, for the increased taxes occasioned by the construction of new or added buildings, structures or other improvements on the property from the date when the improvement was substantially completed or initially used to December 31st of that year.  This allows for the owners and occupant of new construction to pay taxes for the value of their property for the part of the year that it was owned, completed, and occupied.  The Supervisor of Assessments Office can answer any further questions on this subject by calling (815) 319-4460.