No. All terminated employees do not need to be reported on the Form 8955-SSA. Only those employees who have a vested account balance or vested accrued benefit in the plan.
For example, if an individual with a vested account balance in a 401(k) plan terminates employment in 2011 and receives his entire vested account balance in 2011, the individual would not need to be reported on the Form 8955-SSA. However, if this individual does not receive his vested account balance by the time the 2012 Form 8955-SSA is due, the individual would need to be reported on the Form 8955-SSA.
As another example, if an individual retires in 2011 and begins receiving his monthly defined benefit accrued benefit in 2011, then the individual would not need to be reported on the defined benefit plan Form 8955-SSA. However, if this individual did not begin receiving his monthly accrued benefit by the time the 2012 Form 8955-SSA is due, the individual would need to be reported on the Form 8955-SSA.