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.
Whoever possesses a due Nisaab of money, equal to 85 grams of gold or more, and a lunar year passes on it, Zakah becomes due on him for it.
Being so, the questioner should give Zakah on the amount of money that has reached the due Nisaab once a lunar year passes on it. As for the money he has gained during the year upon which a lunar year has not passed yet, he should give Zakah due on it once a lunar year has passed on it; and it is not due on him to pay its Zakah when the lunar year passes on the first amount of money, according to the preponderant opinion of scholars. But if he pays its Zakah along with that of the former at the end of the due lunar year of the first amount of money, it is sufficient for him, and he even receives a greater reward for it, Allaah willing, since it is more beneficial to the poor.
Allaah Knows best.