What causes you to not leave a tip at a restaurant?

I was a server for over 20 years and my family owns a restauraunt as well. Servers get a max of $2.68 (or close to that) per hour in wages and rely on their tips to provide their income - at 99% of the restauraunts in my state. Plus they are required (again at most places) to tip the bartenders, the bus kids and sometimes even the cook. In most cases, the paychecks are barely enough to pay the taxes that are taken out of the check. We almost always had to pay in taxes as well, because the wages are not enough to pay the taxes. At the last three places I served, they would take my sales for the evening and calculate 15%. This is what they told the IRS I made in tips for the night, whether I did or not. Granted, most times it was more than that, but sometimes not. If we made more, we were responsible to turn in the remainder on our own taxes. I can't answer for all servers, but I always turned in the right amount because I was afraid of getting into trouble with the IRS. Even if I get the crappiest of service, I tip 15% because of this. If I get great service, I will tip more than the normal 15%....more like 20 - 30%. Everyone has bad days. The problem with being a server is that you have to be an actress/actor as well. The customers expect a certain level of service and if you are off just a little, it can affect your income greatly in just one day. I know that might sound strange to some people, but it just works that way. I no longer serve because of back and knee injuries. But it was a lot of fun while it lasted. Great topic. It's interesting to see what everyone says. Thanks!!

We usually rate our waiters/waitresses by service and friendliness. We see how many times they come back to refill drinks/coffees and to ensure that our food is good and if we ask them for additional items like silverware, plates etc., we see how long it takes them to return. We've been at restaurants where we never see our server anymore after the food had been served.

we're really not into giving tips here, but in really fancy restaurants, we give at least enough "reward", like 10% of the actual price or keeping changes for their friendliness and accuracy.