I have seen some different opinions on this. ACO Reach does not use the supplemental files; it just uses claim data. I had someone ask about using pseudo claim/penny claims CPT 99499 to add diagnosis codes after the original claim was paid/processed. I had thought the claim would need to be corrected/reopened depending on the MAC process. Has anyone had success doing this? Or do you only use this method if there are more than 12 diagnoses on the claim? There are diagnoses to be added that were found during a review of medical records (as an example). Thank you!