Go to dashboard.stripe.com/dashboard, or click on the Go to Stripe Dashboard button on the Store > Checkout tab.
Click on the Payments tab in your Stripe Dashboard and click on the payment you'd like to refund:
Click on the Refund Payment button at the top right corner:
You can either process a Full refund, or a Partial refund for the client. Refunds usually take 5 to 10 days to appear on their statement:
You can issue a refund at any time up to 90 days after the charge. It becomes more likely that certain circumstances may cause a refund to fail - for example if the card has expired.