When does the hawl for zakat begin on land purchased through tawarruq and sold before the completion of the hawl? Is zakat obligatory on its value while it is still being paid in installments? And if its value is added to purchase new land for the purpose of building and leasing, is zakat obligatory on the value of the new land or on its rental value?

Zakat on trade goods becomes obligatory if they reach the nisab (minimum threshold) and a full year (hawl) has passed since the original capital used to purchase them came into your possession. The hawl for land is reckoned from the time its price enters your ownership. As for the remaining value of the land after its sale, its hawl is that of the original capital, meaning the hawl is not interrupted by the sale of the goods. The preponderant opinion is to pay Zakat on all the money in your possession without deducting debt. If the land was purchased with the intention of building on it, there is no Zakat on it because it is not considered trade goods. However, if it is rented out, Zakat becomes obligatory on its rent if it reaches the nisab and a full year has passed over it.