If you were promised a certain amount of severance by your former employer and you have not seen that money or have only seen a portion of it, your employer has violated a contract and you can sue for that money and breech of contract.
While severance is not the same as an actual wage-as you did not actually work for that sum of money-the fact that you entered into a contract stating that a certain amount of severance pay would be granted is enough to justify a lawsuit.
The first thing you should realize about severance is that is typically used as a way to soften the blow of losing a job and hopefully--for the company--prevent you from suing for wrongful termination. If you signed a severance agreement, you may have signed over your right to sue the company over issues involving your termination. Do not sign a severance agreement if you feel that you were unfairly let go by your company. But while it may be more difficult to sue for wrongful termination after signing, you can certainly still sue for the severance.
Research laws regarding severance--knowing a little about the law and how it may relate to your current situation can be priceless. Contact your employer and ask about the severance pay you have not seen--it may be a matter of confusion that can be easily cleared up. Consult an attorney--if your employer still refuses to give you the pay you agreed to, it may be time to send a formal letter and then begin a lawsuit.
Whether you were fired for poor performance, laid off, outsourced, or you have resigned, your employing company is fearful of negative publicity, complaints from former employees to board members, the possibility of being sued and the disruptive time and expense of litigation, and anyone speaking ill of the company. Companies want you to go away quietly and stop any possible controversy. All companies expect to negotiate severance packages in exchange for a Separation and Release Agreement, so you will be leaving not only on 'good terms', but also on your own terms!
Most severance packages are provided when companies have no money, file bankruptcy, or simply cut costs through layoffs. In fact, severance packages provided during these unfortunate events are usually more generous.
Human Resources and your boss will push you to take the check they've already cut and sign a release agreement right away. Don't do it as no employment situation is 'take it or leave it'. Tell them you need to think this situation over. They will not, and cannot, withdraw the severance offer-even if you ask for more! In fact, there are federal laws which require them to give you three weeks or up to 60 days to consider the agreement-more than enough time to negotiate a better severance package.
Severance pay entitlement are created and implemented by your friendly Human Resources Department. But, if you hire an attorney to represent you to negotiate a severance deal, your friendly HR Department MUST, and will, turn you and your attorney over to its corporate Legal Department and its attorneys. You will have a tough time negotiating a severance as corporate attorneys always take a tough stance against opposing attorneys. Your matter will be legally escalated into a battle of attorneys. And, it's another story if you launch a lawsuit. The best severance deals come from HR departments.