We are not aware of any UCC provisions or court cases that would prevent you from shortening the notification window for unauthorized checks, particularly for your commercial customers. 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 (provided that the bank acted in good faith and exercised “ordinary care”). 810 ILCS 5/4-406(c), (e). 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). An Illinois court has upheld a 30 day notification window in Napleton v. Great Lakes Bank, N.A., 945 N.E.2d 111, 119 (1st Dist. 2011). Also, that opinion relies on decisions from courts around the country that have upheld even shorter periods, such as 20 days in a Minnesota case, Stowell v. Cloquet Co-op Credit Union, 557 N.W.2d 567 (Minn. 1997), and 14 days in a Wisconsin case, Borowski v. Firstar Bank Milwaukee, N.A., 579 N.W.2d 247 (Wis. Ct. App. 1998). All three cases all dealt with consumer deposit accounts. In the case of a commercial account, you would have even stronger arguments supporting a shorter notification window, as commercial customers generally are considered to be more sophisticated than consumer customers.