If your letter of termination indicated pay in lieu and also severance. Is it dependant on the Release letter they provide?

The titles given to the payments, ultimately, do not matter. What is important is to determine whether you have been offered proper compensation. The amount you are owed is based on your age, length of employment and position. To see how much you are owed, use the Severance Calculator and then give me a call: www.severancepaycalculator.com
Lior Samfiru