QuickBooks Online is equipped with tons of different reports that you can use to get a snapshot of your business. You can run the Audit Log report for the transaction and filter it to show deleted/ voided transactions in QuickBooks Online.
Here's how to pull up Audit log report:
Go to the Gear Icon.
Choose the Audit Log.
Select the Transactions.
Drop-down arrow under Show: Deleted/ Voided Transactions.
You can browse these articles to learn more about what the audit log can do and how to use it: