All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Property of an investment company or organization is liable for Zakah(Alms) as one unit. Therefore, all shares are liable for Zakah asone big share once they reachNissab(Minimum amount liable for Zakah)and a full lunar year elapses over possessing them; even if some of themhaven`t reachedNissab.Narrated Anas: "Abu Bakr wrote to me what was made compulsory by Allah's Messenger (PBUH) and that was (regarding the payments of Zakat): Neither the property of different people may be taken together nor the joint property may be split for fear of (paying more, or receiving less) Zakat."{Related by Bukhar}.
Al-Imam Ibn Hajar (May Allah have mercy on him) said, "The reliable opinion of the Shafie school of thought is that the property owned by different individuals is treated as one unit/amount in terms of liability for Zakah."{Tohfat Al-Mohtajj, 3/259}.
However, the majority of the scholars are of the view that the mixing of the shares doesn`t make them one big amount, i.e. each shareholder must pay the Zakah due on his share if it reaches Nissab and one full lunar year elapses over possessing it. If it didn`t reachNissab, no Zakah is due on it.
In order for the above organization to pay the Zakah due on its property, it must pay (2.5%) for all its assets; be they cash, commodities or debts that have already passed their due date. This is to the exception of fixed assets as they aren`t liable for Zakah.Either the shareholders delegate the organization to pay the Zakah on their behalf and deduct it that amount in accordance with the share of each, or that the shareholders pay it themselves.
In conclusion, to be on the safe side and cleared from any liability, one should follow the view of the Shafie jurists. However, there is no harm in following the opinion of the majority of the scholars. And Allah knows best.