Would my wife be informed by my bank that I have credit card charges for hotel stays with my girlfriend? As pointed out by Hansi and Cuch, the way you ask the question suggests that you know you are thinking about doing something you shouldn't be doing. If this is really not competing and it is really in your spare time, just ask your boss whether it is OK. He may surprise you and say yes. If you were planning to spend some weekend time to help out a friend to launch his Raspberry Pi educational product suite in exchange for a free lunch and some stock options, you would probably just do it and maybe mention it in passing to your firm (my firm would have a long and painful compliance process, but they would sign off on it in the end -- this one, definitely not).