Hello there, Rcsllc21.

May I know if the paid credit card transaction was downloaded from your bank? If so, we can match this transaction to your invoice and process a refund to return the money to your customer.

Please note that this process is only applicable for unpaid invoices within QuickBooks Online.

Here's how:

1. Go to the My Apps tab, Accounting, and click Bank Transactions.
2.  Select your connected credit card bank account
3. Under the For Review section, click on the transaction to expand its details, and then select the Match button.
   
   
4. Review the transactions under the Find Other Matches to locate the matching invoice.
5. Select the transaction that matches the bank feed entry, and click Save to confirm.
   
   

However, if you had set up the payment through the integrated QuickBooks Payments, follow the steps below:

1. Sign in to your QuickBooks Payments account.
2. Select Reverse a Transaction from the Processing Tools menu.
3. Fill in the necessary fields and select Search.
4. Select the Auth Transaction ID(s) for the payment(s) you wish to refund (not the Capture ID).
5. Select Submit.

Additionally, for information about alternative refund processing methods, please refer to this page: Void or refund transactions in QuickBooks Payments.

Please let me know if you have any other concerns.