As a matter of public policy, CA courts have held that an employee cannot waive his or her right to assert a claim for unpaid overtime by signing a severance agreement. You'd be very wise to immediately consult with an employment law attorney to assist you in the enforcement of your rights.
This answer is a general interpretation of the law and is not fact specific to your case. Likewise it does not create an attorney-client relationship. You should seek an attorney for a review of your specific facts and documents.
If you were paid money that you were not otherwise owed for wages or vacation payout in exchange for the severance agreement, then it is likely enforceable against you and you have released the employer of any claims you might have had against it.
If you were not paid money separate from what you were owed at termination, then the severance and release will be unenforceable.
You should locate and consult with an experienced employment law attorney as soon as possible to explore your facts and determine your options. I would suggest you look either on this site in the Find a Lawyer section, or go to www.cela.org, the home page for the California Employment Lawyers Association, an organization whose members are dedicated to the representation of employees against their employers.
Good luck to you.
This answer should not be construed to create any attorney-client relationship. Such a relationship can be formed only through the mutual execution of an attorney-client agreement. The answer given is based on the extremely limited facts provided and the proper course of action might change significantly with the introduction of other facts. All who read this answer should not rely on the answer to govern their conduct. Please seek the advice of competent counsel after disclosing all facts to that attorney. This answer is intended for California residents only. The answering party is only licensed to practice in the State of California.
An employer can't waive overtime rights under the federal Fair Labor Standards Act, except through a court-approved settlement or a settlement through the US Department of Labor.
My answers to questions posted on AVVO are intended to provide general information only, and are not intended to be legal advice. Employment law issues typically require a careful case-by-case analysis. Consequently, if you feel that you need legal advice, I would encourage you to consult in person with an employment attorney in your area.
IF your wage claim for overtime was in dispute, then the release would prevent you from suing for overtime. If not, you may have a valid claim for overtime pay going back at least 3 years plus 10% interest plus up to 30 days' pay as a penalty, PLUS your former employer, according to the law, "shall" pay your attorney. Call an employment law attorney to discuss. Many offer a free initial phone consultation and may be able to get what is owed to you (assuming you were nonexempt, worked OT without OT pay and did not release a disputed wage claim by the release) without cost to you.
Typically, severance agreements releasing employment claims are enforceable. People are charged with knowledge of what they sign, unless it is written in a language they are not familiar with or they have a very limited education. Assuming you can prove that the severance agreement was presented as take it or leave it with only an hour to decide, so you did not have the opportunity to read, understand and review the document with counsel of your own choice, you raise some thorny ethical and legal issues. I am not confident they are enough to invalidate the release.
Please note there special rules regarding the validity of releases of age discrimination claims, which require a minimum number of days for you to consider the release and give you the option to revoke the release for an additional number of days. Finally, workers compensation claims cannot normally be released without approval of the worker's compensation appeal board.