How is zakat to be paid on money invested in installments from one's salary, while there are unpaid installments? Is it due on the principal, or the profits, or both, along with the salary? Is it due upon its hawl (completion of a lunar year)? Is it permissible to pay it in advance? Is zakat due on loan money? Is it permissible to give zakat to one's widowed grandmother?

Zakat on wealth is obligatory if it reaches the nisab (minimum threshold) and a full lunar year (hawl) passes over it. For trade goods, the hawl is based on the original capital used to purchase them. The profit from trade is added to the principal, and a quarter of a tenth (2.5%) of the total is paid as zakat. As for the money earned from salary during the hawl, it has a separate hawl according to the majority of scholars, or it can be paid with the principal for ease. Zakat on due installments and debts is obligatory; it is permissible to delay paying it until it is received, then pay zakat for the past years. It is not permissible to deduct debt from zakat-eligible wealth, based on the more cautious opinion. It is permissible to pay zakat in advance during the hawl. It is not permissible to give zakat to one's grandmother, according to the majority of scholars, due to the obligation of her maintenance falling upon the zakat payer.