10 ILCS 5/17-16
If the voter marks more candidates than there are persons to be elected to an office, or if for any reason it is impossible to determine the voter's choice for any office to be filled, his ballot shall not be counted for such office, provided that if the name of a candidate appears in more than one column on the ballot as authorized by this Act, and a ballot has been marked in his or her favor in more than one column and the voter's intention is otherwise ascertainable, the candidate shall receive only one vote from such ballot and the remaining votes cast for him or her on such ballot shall not be counted. No ballot without the official endorsement shall be deposited in the ballot box, and none but ballots provided in accordance with the provisions of this Act shall be counted. Ballots not counted shall be marked "defective" on the back thereof, and ballots to which objection has been made by either of the judges or challengers shall be marked "objected to" on the back thereof, and a memorandum signed by the judges stating how it was counted shall be written upon the back of each ballot so marked, and all ballots marked defective or objected to shall be enclosed in an envelope securely sealed and so marked and endorsed as to clearly disclose its contents. The envelope to be used for enclosing ballots marked "defective" or "objected to" shall bear upon its face, in large type, the legend: "This envelope is for use after 7:00 P.M. only." The envelope to be used for enclosing ballots spoiled by voters while attempting to vote shall bear upon its face, in large type, the legend: "This envelope is for use before 7:00 P.M. only." All ballots not voted, and all that have been spoiled by voters while attempting to vote, shall be returned by the judges of election to the county clerk and a receipt taken therefor, and shall be preserved 2 months; the county clerk shall keep a record of the number of ballots delivered for each polling place, the name of the person to whom and the time when delivered, and he shall also enter upon such record the number and character of ballots returned, with the time when and the person by whom they are returned.
10 ILCS 5/17-16