Severance agreement arrived, need a second opinion - what worked for you?

My manager said the package is final, but the letter gives me time to review. It has been weighing on me all week. I do not want to leave money on the table. Did anyone negotiate and succeed?

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.

Ask for the offer in writing and do not sign on the spot. A day or two to think is normal.