Please note that this answer discusses the requirements of the Check Printer and Check Number Act before it was amended in 2014. For a current version of the law, please see 205 ILCS 690/10.

Illinois law requires checks drawn on a consumer deposit account to include the month and year the account was opened and a check number. This requirement does not apply to temporary checks provided by a bank when opening a consumer deposit account. 205 ILCS 690/10.