What is the amount of annual Zakat due on the profit from the business of selling apartments, knowing that a portion of the profit is saved and invested in renting out other apartments for living expenses, and that the working capital does not complete a full hawl (lunar year)?

Zakat must be paid on the value of apartments, building materials, and lands prepared for trade at the end of each Hijri year. The value of these trade goods is calculated in addition to the cash capital if it reaches the nisab and a year has passed over it. As for apartments prepared for rent, Zakat is not obligatory on them; rather, it becomes obligatory on the surplus rent after it is received and a year has passed over it.