Years ago, we had one of these "helpful" guys at work. When a bunch of us went out to lunch together, he would divide the tab and tip by one less than the number in the party, giving himself a free ride. Then he'd pocket the cash and put it on his credit card. Come tax time, he would deduct it as a business expense. I don't remember how we found out, but we did. He didn't get a beating, but he was very lonely after that.