1. Log in to your admin panel
  2. Click "Reports" in the left sidebar
  3. Open the "Participants" folder and click "Registrants with Reg Fields, Donation and Contacts Summary"
  4. Click "Run Report" in the top left of the report tab
  5. Scroll across to find the "Discount Code" column
  6. Click on the arrow next to the top of the column, and click "Group by this field"
  7. All registrants who have used discount codes will now be grouped together at the bottom of the list