Depends on how much was vested, and how much prior work was done, and how much of a hardass you want to be. You're under no legal obligation to return it, but y

Depends on how much was vested, and how much prior work was done, and how much of a hardass you want to be. You're under no legal obligation to return it, but you might want to in some scenarios. Let's say you had 2 co-founders and you all vested 33/33/33. I would personally feel unethical about keeping the equity if I left after 6 months. At that point, you're now free-riding on the remaining co-founder FUTURE work. Furthermore, you keeping that much equity will screwing the company (and yourself) since it will limit ability to raise money, bring on key executives, open up an option pool. In this case, I'd return a good chunk (but not all) of the equity. BUT if the equity vested was really for PAST work, as you imply here, then yeah, keep the equity.