A method is provided of operating an image-based check processing system to detect a double feed condition of carrier envelopes. An example method includes attempting to read a magnetic ink character recognition (MICR) codeline from a first predefined area of an image of a document item, determining if the document item is a carrier envelope, concluding that the document item is not a double-fed item when a determination is made that the document item is a carrier envelope, and concluding that the document item is potentially a double-fed item when a determination is made that the document item is not a carrier envelope.