If you need to refund one of your customers for a Partial.ly payment, you can do so from the Partial.ly merchant portal.
Login to your Partial.ly merchant portal and select the payment plans section. Select the payment plan from the list containing the payment you want to refund. On the payment plan details page, scroll to the bottom to find the Payments section. Here, you'll see a list of all the payments for payment plan. Simply select the refund button next to the payment you want to refund.
You can refund the full payment, or any amount less than the full payment by typing the value in the text box.