Therapists are sincerely appreciative and grateful when they receive a gratuity after giving a massage. Leaving a gratuity is a way to thank them for their service, just as you do any other licensed professional. It is a very common practice in this service business. While most will be paid by the massage, the gratuity is an additional amount that will indicate your satisfaction with their service. Suggested amounts are 15-20% and should be based on the full price of the session, just as you would do if you were using a coupon or gift certificate for a meal.