735 ILCS 5/1-109
Unless otherwise expressly provided by rule of the Supreme Court, whenever in this Code any complaint, petition, answer, reply, bill of particulars, answer to interrogatories, affidavit, return or proof of service, or other document or pleading filed in any court of this State is required or permitted to be verified, or made, sworn to or verified under oath, such requirement or permission is hereby defined to include a certification of such pleading, affidavit or other document under penalty of perjury as provided in this Section.
Whenever any such pleading, affidavit or other document is so certified, the several matters stated shall be stated positively or upon information and belief only, according to the fact. The person or persons having knowledge of the matters stated in a pleading, affidavit or other document certified in accordance with this Section shall subscribe to a certification in substantially the following form: Under penalties as provided by law pursuant to Section 1-109 of the Code of Civil Procedure, the undersigned certifies that the statements set forth in this instrument are true and correct, except as to matters therein stated to be on information and belief and as to such matters the undersigned certifies as aforesaid that he verily believes the same to be true.
Any pleading, affidavit, or other document certified in accordance with this Section may be used in the same manner and with the same force and effect as though subscribed and sworn to under oath, and there is no further requirement that the pleading, affidavit, or other document be sworn before an authorized person.
Any person who makes a false statement, material to the issue or point in question, which he does not believe to be true, in any pleading, affidavit or other document certified by such person in accordance with this Section shall be guilty of a Class 3 felony.
735 ILCS 5/1-109