A study at Cornell University found customers are leaving well over 15-18 percent.
The survey checked 9,000 credit card receipts in the New York area. More than one-third of customers left their servers close to 25 percent.
More businesses are also putting out tip jars, and posting signs inviting a gratuity.
Itipping.com suggests, 20 percent if your server did a good job, more if the meal includes wine and 5-10 percent in a tip jar.