I'm here to help provide some insights about your bill overpayment in QuickBooks.
A credit memo is issued in order to reduced the amount that a customer owes from a previously issued invoice. In your case, you shouldn't be creating a credit memo, instead, you'll need to enter an expense.
You'll need to post this to Accounts Payable so you can either issue this as a refund or a credit you can use for the next bill payment.
Here's how to enter an expense:
On your QuickBooks account, go to the Plus Icon and click Expense.
Select the Payee and Payment date.
On the Category details, select Accounts Payable and enter the amount.
Once done, click Save and close.
Later on, you can add this expense if you want to create a check refund or you can apply this on the next bill payment.