It depends. If you are already legally entitled to severance (for example, because it was promised in your employment contract or employee handbook), then your employer may not force you to sign a release to get it. However, if you aren't already legally entitled to severance, or if your employer is offering you additional benefits for signing a release, that may be perfectly legal. A release requires you to give up your right to sue your employer. Before you sign one, you should understand exactly what rights you are giving up and what you are getting in return. For more information, see Nolo's article Should You Sign a Release When You Lose Your Job?