Do I lose my employer match if I leave before I'm fully vested?

You keep 100% of your own contributions and their earnings no matter when you leave, but you forfeit the unvested portion of employer contributions. For example, on a 20%-per-year graded schedule, leaving after three years means you keep 60% of the match and give back 40%.

Before resigning, check exactly where you sit on the schedule; staying a few extra weeks to cross a vesting anniversary can be worth thousands. Note that many plans measure vesting by years of service that may hinge on hours worked or plan-year boundaries, not your exact hire date, so confirm the crossing date with HR. Forfeited amounts typically go back to the plan to reduce future employer costs, per Department of Labor rules.