5 ILCS 260/10
When a surety upon the official bond of any state officer or agent, county, town, city, village, incorporated town or other public officer, or the heir, executor or administrator of such surety, desires to be released from such bond, he may give notice in writing to the officer upon whose bond he is surety that he desires to be so released, and that such officer give a new bond with sufficient sureties within ten days after receiving such notice, and may within five days after the service of such notice deliver a copy of the same, with an affidavit showing the time and manner of service, to the court, officer, or board authorized to approve the bonds of such officers. And if such officer shall not within ten days after receiving such notice, or within such further time, not exceeding twenty days, as the court, officer or board shall allow, give a new bond with sufficient security, approved as required by law, his office shall become vacant, and the vacancy shall be filled as provided by law.
5 ILCS 260/10