To print a Receipt for a Client when charging a credit card, you would select Print Receipt in the Accept a Payment popup window.

You can only print the receipt while in the Accept a Payment window. Both the saved payment method and the new payment method will allow you to print a receipt.

When you click "Click to Process Payment" the payment will process and a new window will appear with the receipt. Press Control + P or right-click and click Print to print the receipt.