Payment Receipt Printing
If you would like to print receipts for payments, activate the Payment Receipts add-on (Tools -> System -> Add-ons). After entering in info for a customer payment, you will have a button to print a receipt. The receipts are 2.5 inches wide.
You can reprint payment receipts by going to Income -> Reports -> Billing -> Payment Report. Click the value in the Payment Method column to reprint the payment's receipt.