805 ILCS 310/4
Duplicate originals of the articles of incorporation shall be delivered to the Secretary of State. If the Secretary of State finds that the articles of incorporation conform to law, he shall, when all franchise taxes, fees, and charges have been paid: (a) Endorse on each of such duplicate originals the word "Filed," and the month, day, and year of the filing thereof; (b) file one of such duplicate originals in his office; (c) return a true copy of the articles of incorporation to the incorporators or their representative, who shall within 15 days file such document for record in the office of the recorder of the county in which the registered office of the corporation in this State is situated. Upon the filing of the articles of incorporation by the Secretary of State, the corporate existence shall begin, and such articles of incorporation shall be conclusive evidence, except as against the State, that all conditions precedent required to be performed by the incorporators have been complied with and that the corporation has been incorporated under this Act.
805 ILCS 310/4