Thanks for posting in the Community. I'm here to lend a hand with deleting a deposit.
Here's how to delete a deposit in QuickBooks Online:
Open up the deposit.
Click Yes to confirm that you want to delete it.
The following is a video to serve as a visual reference:
While this will remove the transaction from your books, there will still be a record of it in the Audit Log. For additional information on this feature and how to use it, please see the following article: The Audit Log: What It is, How to Use It.
That's it. These steps should help you to delete the deposit.
I'm just a post away if you should have any questions. Have a good day.