If the check is payable to a business, and the improper endorsement does not change the check’s payee (i.e., it is an endorsement in blank), your bank most likely could rely on the depositary bank’s presentment warranties, as discussed above. While your customer could argue that your bank should not have paid a check with an improper endorsement because it is not “properly payable” under the Uniform Commercial Code (UCC) (810 ILCS 5/4-401National Bank of Monticello v. Quinn, 126 Ill.2d 129, 139 (1988)), the UCC also requires a depositary bank to warrant that any indorsements on checks it presents for payment are valid. 810 ILCS 5/3-417810 ILCS 5/4-208First Nat. Bank of Chicago v. MidAmerica Federal Sav. Bank, 303 Ill.App.3d 176, 181 (1st Dist. 1999).  Consequently, if your customer objects to the payment of a check with an invalid endorsement, the customer would be entitled to demand repayment from your bank, but in turn your bank would be entitled to demand repayment from the depositary bank for the amount of the check.