A method is provided of operating an image-based check processing system to detect a double feed condition of checks. The method comprises attempting to read a magnetic ink character recognition (MICR) codeline from front of a check item. The method also comprises electronically by a rear imaging camera, capturing image data which is representative of a rear image of the check item as the check item is transported from an upstream end of the document feed path to a downstream end of the document feed path. The method further comprises alerting an operator when information from the attempted read of a MICR codeline from front of the check item and information from the rear image of the check item meet predetermined criteria which is indicative the check item comprising two overlapping checks.