A tip is definitely appreciated in the corporate world but not really required. Aside from flying the airplane, corporate pilots are also responsible for putting your bags in the belly of the jet as well as fetching them once you land (in all weather conditions). In addition, many small private jets do not have flight attendants so the first officer may pick up those duties on occasion. I have a few close friends who fly corporate jets and they receive tips all the time. Most are paid an annual salary and not by the flight hour like airline pilots. They are not filthy rich like some may believe, they work very hard and have extremely erratic work hours. In a sense it is a service industry style flying job. Like I said, tipping is not required and they aren't expecting it and will likely not accept it. If you feel you want to tip, then by all means, go for it.