Thanks for checking in with us, Gerard62.
I'd be pleased to share with you the steps on how to delete a credit memo in QuickBooks Desktop. Here's how:
- Click Customers at the top menu bar and choose Customer Center.

- Go to the Transactions tab and select Credit Memos.

- Find and double-click the credit memo you want adjust or delete.
- Edit the amount or click the Delete button.

To know more about credit memos and refunds work in QuickBooks, check out the following article: Give your customer a credit or refund in QuickBooks Desktop for Windows. This will provide you with steps on how to handle as well as apply the transaction to an invoice.
Feel free to get back to me if there's anything else you need. I'm more than willing to lend you a hand. Have a nice day!