When refunding from a credit balance, only a full refund is allowed. There are no options for refunding a certain amount and retaining the rest of the funds for your organization. To get around this problem a "dummy" season and session are needed. First, create a new Season by following the steps in Creating a Season. Make an internal only session and price it according to whatever funds you need to keep from the credit balance. Then, follow the below steps to apply the credit balance and refund the rest back to the customer:
  1. From People search for participant's record and open 
  2. Click Register at top right
  3. Choose participant to register
  4. Select "dummy" season created earlier and Continue
  5. Select "dummy" session created earlier and Continue
  6. Continue on next screen without answering questions
  7. Under Payment method click Credit Balance 
  8. Click Complete order
  9. Process refund from credit balance as normal
If you are refunding from a session directly and not from a credit balance, you should follow this instead: Partial Refunds