Negotiate Your Severance

The call came this morning, and now there is a document on your screen with a number in it and a deadline at the bottom. HR used the word "standard." Your rent is due, the clock is running, and every line of the agreement seems to say that you release, you waive, you agree. Should you just sign and take the money? What are you actually giving up? Can you ask for more without losing the offer? And ...