It important to know that you can only change the payment date for offline transactions (cash and check). There is no option to change the payment date for all online transactions.
  1. Navigate to Communities > Special Events > Friends Asking Friends > Kintera Thon
  2. Hover over the Event Name > Click Bookkeeping > Manage Initiative Records
  3. Search for the existing participant > Click Edit
  4. Click Edit Registration Information page
  5. Change the Fee and the Payment Type if needed
  6. Add check number, etc
  7. Click Save

If you are unable to update the Payment Date, Chat With Support and reference this article. 

**In order to have the Payment Date changed for a group of records, you would need to submit a spreadsheet with the Supporter ID, Payment ID, what the Payment Date currently is, and what the Payment Date should be.