All perfect praise be to Allah, Peace and blessings be upon Prophet Mohammad.
Flats set for trade are amongst the items of merchandise on which Zakaat (Obligatory charity) is due. It is to be paid after one lunar year elapses over possessing the capital with which they were purchased, or built i.e. the lunar year commences from possessing the capital, and not from the founding of the enterprise, or saving money for it. Therefore, the unsold flats are assessed according to their average price value, on the day when their Zakaat is due, which is added to the cash available in the company, then (2.5%) of the total amount is paid as Zakaat.
As for the flats sold by installments, Zakaat is only due on them after collecting each.
It should be noted that the lunar year could elapse on the company`s capital before selling the flats, but this doesn`t free it from the liability of paying the Zakaat instantly after the end of that year since it is due on capital by the end of every lunar year.
Accordingly, it is easier, for calculation and more valid for the Zakaat giver, to estimate the average price value of these flats, and to deduct (2.5%) of that value, then pay it from the sum of the first sold flat so that no Zakaat remains due on him. However, it is permissible for him to delay the Zakaat, provided that it is paid before the end of the lunar year.
As regards rented flats, no Zakaat is due on their value, rather, it is due on their rental income provided that it reaches Nissab and a whole lunar year elapses on it. This is based on the Prophet`s (PBUH) saying: “ A Muslim isn`t obliged to pay Zakaat on his slave, or on his horse.” {Bukhari&Muslim}.This narration is an evidence that there is no Zakaat on the money [wealth] from which a person benefits and which isn`t set for trade. This is the view of the four juristic schools. And Allah knows best.