35 ILCS 200/10-185

When initial mining commences after the assessment date, or when all mining ceases prior to the end of a calendar year, the coal as assessed pursuant to Section 10-180 shall be assessed on a proportionate basis in accordance with Section 9-180. For purposes of this Section any permitted acreage that is to be mined during the current year which is not included in the anticipated 5 year mine acreage due to a change in the mining plan shall not be subject to assessment on a proportionate basis in accordance with Section 9-180.