Is zakat obligatory on the fluctuating capital of a real estate company, and when is it due?

If the money in the account reaches the nisab (the value of 85 grams of gold or 595 grams of silver), zakat becomes obligatory on it every year (hawl). If the money falls below the nisab during the year, a new year is calculated from the time it reaches the nisab again.

Zakat is paid by determining the day, according to the Hijri calendar, when the money first reached the nisab. When the same day arrives in the following year, all the money in the account, along with its profits, is subject to zakat at a rate of 2.5%, and it is combined with any other zakat-eligible money owned by the muzakki (the one paying zakat).