All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
If your money reaches the Nisaab (i.e. the minimum amount liable for Zakah) and a lunar year has elapsed on it, you are obliged to give the due Zakah on it and you need not pay any additional amount as an act of caution. Still, you are allowed to do so and it constitutes an increase of goodness and benefit for the poor. You will thus receive the reward of voluntary charity, which is commendable according to the more correct opinion. Another view regards the payment of both amounts as obligatory as stated by Imaam An-Nawawi . And Allaah The Almighty Does not Cause the reward of those who do good to go to waste.
Allaah Knows best.