70 ILCS 605/5-31
If, at any time, the ownership of any tract of land is divided in a manner other than that described in any assessment roll and such assessment, or a portion thereof, is unpaid, the landowners may agree upon the division of the assessment or the unpaid portion thereof between or among them and request the division of the assessment on the district collector's books. If the request for division of the assessment is approved by the commissioners, they shall adopt a resolution granting the request and file the same with the Clerk, who shall record it in the drainage record. The district collector, upon receipt of a certified copy of the resolution, shall make a division of the assessment or the unpaid portion thereof on his books to correspond with the agreement of the landowners, and such divided assessment shall thereafter be enforceable only against the separate tracts according to the method of division. Annual maintenance assessments may be divided between or among several owners in the same manner as is hereinabove provided for other assessments. In the absence of such agreement, the district collector shall divide the assessment, or the unpaid portion thereof, on his books to correspond to the ratio of the assessed land area held by each owner after division of such tract to the total original assessed land area of the tract.
70 ILCS 605/5-31