This happens when the option in the TeamRaiser events to send a PDF receipt is enabled. To turn this off:
  1. Find and edit the desired event.
  2. Go to step 3, Select Event Options.
  3. Click on the link Edit Advanced Options on the bottom left hand corner.
  4. Find and unmark the check box "Yes, disable PDF receipts for participants who make an extra gift or donation to themselves at the time of the donation" which is near the end of the page.
  5. Click the Save or Next button to save.
When this check box is checked, the system assumes you are also going to be sending PDF receipts through Receipt Manager and thus shouldn't list the tax deductible portions twice. If you are not sending PDF receipts though, this can be problematic.