All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There are two types of wealth which are subject to the payment of Zakaah:
The first type requires Zakaah to be paid every year such as gold and silver, or similar items, like cash money, trade commodities and cattle (cows, sheep, goats and camels).
The Zakaah of this kind must be paid on yearly bases for the meaning of the Hadeeth of the Prophet which reads: “No Zakaah is due on any wealth unless a whole lunar year elapses on it.” [Ibn Maajah, As-Sayooti and Al-Albaani]
The second category of property for which Zakaah must be paid include items which are weighed and stored such as grains, fruits, farm products and minerals, etc; their owner must pay the Zakaah on them when he collects them and provided they reach the Nisaab (minimum amount liable for Zakaah). When the owner pays the Zakaah on such items, he is not required to pay it again no matter how long he owns it. The time period of one year does not apply to items in this category. However, a person is obliged to pay Zakaah whenever he gets a new Nisaab [in new items] even if this happens in the year many times.
The difference between the two categories of wealth is that the first category is subject to be increased, as the animals reproduce (bear offspring), and so, they bring many benefits to its owners. Similarly, trade commodities, gold, silver and cash money may bring benefits.
It is for this reason that it is an obligation to pay Zakaah on the first category every year, because it is believed that in the period of a year this wealth may be increased. As regards the farm products and fruits, then after paying Zakaah on it, it decreases and it does not increase, and it is for this reason that it is only a must to pay Zakaah on them once. This is indeed from the mercy of our religion as it safeguards the benefit of all the people, the poor as well as the rich.
Allah knows best.