Could you please guide me on how to process a partial refund for an invoice that has already been paid?

To issue a partial refund in QuickBooks, you'll follow different steps depending on whether you're using QuickBooks Online or QuickBooks Desktop. I'll provide the instructions for both versions, nicholas.

To start, if you're using QuickBooks Online, you can follow these steps:
 

1. Go to the + New button.
2. Select Refund receipt.
3. Click the customer who is receiving the refund.
4. Fill in the necessary details, including the date of the refund and the refund payment method.
5. Under the Product/Service column, enter the partially refunded items and adjust the quantity or rate to reflect the partial amount.
6. Save and close the refund receipt.

Moreover, to record the refund, please be guided by the steps below:

1. Go to Sales from the left-hand navigation menu.
2. Select Customers at the top.
3. Find and tap the customer's name.
4. Locate the Refund Receipt and ensure that it reflects correctly.

Finally, if you're using QuickBooks Desktop, here's the guide you can follow:
 

1. Open QuickBooks Desktop and log in to your company file.
2. Go to the Customers menu and select Create Credit Memos/Refunds.
3. Choose the customer who is getting the partial refund.
4. Enter the items or services that are partially refunded and adjust the quantities or amounts as needed.
5. Save the credit memo.

After that, proceed with issuing the refund:
 

1. A popup will appear asking if you want to issue a refund or retain as available credit.
2. If issuing the refund, select Give a refund.
3. Select the refund method (e.g., check or credit card).
4. Fill in any additional necessary information and process the refund.
5. Save and close.

To learn more about the refund process, refer to this article: Void or refund customer payments in QuickBooks Online. You can use it as a guide.

Additionally, here's an article you can use to learn how to send statements to show customers summaries of their invoices, payments, credits, and balances: Create and send customer statements in QuickBooks Online.

Always double-check refund details before issuing them to avoid discrepancies. For any questions about a partial refund or other matters, please let us know in the comment section below.