There is a number on your 401(k) statement that is not actually your money.
Most people never notice it. It sits a few lines below the big balance, in smaller type, labeled something like "vested balance." And for years those two numbers are different.
Then you get a better offer somewhere else. You give notice. You feel great.
And roughly four weeks later, your balance drops by several thousand dollars and nobody sends an apology.
That is forfeiture. It is completely legal, it was in the plan documents you never read, and it costs American workers billions of dollars a year.
Here is how it works, and how to not be the person it happens to.