Let's say that you normally tip at least 20%, and you receive poor service in a restaurant and want to tip 10% instead. Are you ethically obligated to let the waiter or manager know that you were dissatisfied with the service, or does the tip speak for itself? There are times when I want to tip less, but I don't want to have a big confrontation with the staff (either because I know if would ruin the whole experience for my dining companions, or because I am in a hurry and simply do not have time to track down elusive staff and then deal with the issue). But then I wonder how the waiter will interpret a lower tip--will he realize that the service was subpar? Or will he just assume I am cheap? And even if he assumes the worst (of me, not his service), does that really matter, since I am entitled to tip accordingly if the service is bad? My problem is, there have been situations in which I have been reluctant to confront the waiter or management about problems, and also reluctant to be misperceived as cheap, so I pretty much always end up leaving at least 15% even if the service is terrible, simply because I don't want to deal with the situation. Any thoughts about this issue?