Follow the steps below How to Delete a Credit on Quickbooks invoice:
Step 1: Open QuickBooks and navigate to the transaction history by pressing Ctrl + H at the same time.
Step 2: Double-click the invoice from which you want to remove the applicable credit and then click Apply credits.
Step 3: In the previously applied credits window, clear the credit selection.
Step 4: Click done on the Apply credits window and then save and close the invoice in the fourth step.