Yes, you can essentially click the "undo" button if you've applied an available credit in TermSync to a specific invoice by mistake.
1. Start in your account statement which you can navigate to from the top menu.
2. Click on the invoice number that you've applied the credit/credits to.
3. Within the invoice, find Other Related Transactions and click on the correlating number.
4. Your first option under Available Actions will be to unapply the credit. Click on this option.
5. Submit the reason you are unapplying the credit and click Unapply Credit.
6. Look for the confirmation popup across the top of the screen. Navigate back to the Account Statement to see the credit/credits in your account statement, unapplied.