You will need to refund the total amount paid to all payment methods and leave the check open. Then you can remove the gratuity from the 'Gratuity' button in the order view. After all payments are refunded, remove the gratuity the same way its applied. From Pay>Gratuity>Remove: After all payments are refunded, remove the gratuity the same way its applied. From Pay>Gratuity>Remove: