Apply credit memo to invoice already paid - invoice was incorrect
I was checking through and reading the posts before posting online. I realize I may be repeating but I'm not sure quite how to do what was suggested. I created an invoice for $378 and when the products were delivered, not all of the product was received by the customer at location A. Due to communication errors, the invoice was not adjusted before sending for payment. The customer paid the full amount of the invoice four months ago and the error was discovered when their systems were synced.
On the most recent payment from the customer, location B received full payment, however they reduced the check by $108 for location A. Applying the amount for location B is not a problem, but I am not sure how to adjust for an incorrect invoice. I thought I could create a credit memo however there is nothing to apply the credit memo to for the receivables. I thought about adjusting the invoice, but that would not work as it would not be correct as well. Based on scenarios for QBO, there were other options available but did not appear to work for the desktop or I might have gotten confused along the way.
Thank you for the consideration and I look forward to any help you guys can provide.