Processing duplicate items in image cash letter (“ICL”) return files for efficient handling. A duplicate item processing module can receive ICL return files comprising items representing duplicate electronic checks. The duplicate item processing module can determine whether the processing entity erroneously presented the item more than once. The duplicate item processing module can also determine whether the depositing institution erroneously deposited the item more than once for processing. Based on the determination of the source of the error, the duplicate item processing module can make a correction in its own records and/or forward the ICL return file with the duplicate item to the depositing institution.