Hi there, hughie85-me-com! Great to see you around!
If you mean, placing "CR" beside an amount, we're unable to that. However, you can create an adjustment note and email it to your customer if you want to show you're giving them credits. This is a stand-alone transaction, by the way.
If your customer has overpaid and incurred credit in their profile, you can send them a statement.
Let me know if you have more questions.