On the ‘New Payment’ screen, simply enter the customer’s e-mail address and a receipt will automatically be e-mailed to them when the payment is processed.
Note: You will need to have Emails turned on in your Stripe account, which you can activate at https://dashboard.stripe.com/account/emails.
If you would like to customise your receipts (we recommend you do) to include your company logo and change colours etc, simply follow the instructions provided here.