Level 1

Add a line to an bundled invoice that is a credit amount

I would like to add a line to one of my bundled invoices  in Quickbooks Online.  The line I want to add is a credit amount.  Can I do this?  I have tried and I am able to add a new line but after I save and close and go back to look at my bundled invoice, the credit line is not there.  I dont want to a credit memo as I have several of them to do.  This would be the easiest way.