We do not believe that the bank would be liable for any forged checks if a customer failed to notify the bank of the forgeries within the thirty-day notification period. Under Section 4-406 of the Uniform Commercial Code (UCC), if a customer does not notify a bank about forged checks with “reasonable promptness,” the bank will not be liable to that customer for the checks (unless the bank failed to exercise “ordinary care”). 810 ILCS 5/4-406(e). Note that banks may narrow the definition of “reasonable promptness” in a deposit agreement, so that customers have only a certain time period in which to report forged checks. 810 ILCS 5/4-103(a). In fact, an Illinois court specifically upheld a thirty-day notification window in a recent case, Napleton v. Great Lakes Bank, N.A., 945 N.E.2d 111, 119 (1st Dist. 2011).