The question is not very clear. Do you mean to say, "Can an employee who has already been advised to leave by the company, with a provided notice period, submit their resignation during that notice period?"
In this case, if a letter is issued to the employee regarding their exit (for non-performance or any other disciplinary issue), then the need for resignation from the employee is not applicable. However, voluntary resignation can be accepted and kept as proof to strengthen the reason for their exit.