When an invoice is fully paid (balance is $0) is marked as paid. The payment will be synced to QuickBooks® where you will see the Paid status on the invoice.
To record a payment you can go through the Main Menu of the app -> Sales -> Customers
Search the customer and tap on it to see the options, select receive payment to see the payment form and then save/send.
To print a receipt is required a custom parametrization according to the brand of your printer. Call us +1 866 5772270 for more information.