You can run a report to see how much you've issued in refunds in QuickBooks Online for any given date range.
- Click on Reports on the left navigation panel
- Type in “transaction list” in the search bar and click on the Transaction List by Customer report
- Click on Customize on the top right
- Select the date range, click on Filter to expand options, and select Transaction Type > Refund and Customer > All
- Run report to see results