On the payment page the Tip section lists No Tip, your preset tip buttons (percentages with the computed amount, or fixed amounts, depending on Business: Cart > Tips - Type (Percentage, Fixed Amount) and the configured tip values) and Other for a custom amount (type it and click apply). The tip is added to the total immediately. On POS orders the tip is attributed to an employee, which can later be changed on the order page (Tip (Paid to: …)).