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.
The "Jam`iah" referred to in the above question is some kind of a lending system to which people resort so they can use the money collected to get married or buy a car or similar things. Sharia frames this as "A presumptive loan". In other words, each member becomes a lender upon paying the monthly installment and a borrower when it is his turn to collect the total sum.
Accordingly, the Zakat of the above installments should take the rulings of the Zakat on debts: If you have received that total sum at the beginning of the rotation, then no Zakat is due on it unless it reached Nisab (Minimum amount liable for Zakat) and one full lunar year elapsed over possessing it.
As for the monthly installments, they are payment of a debt and so no Zakah is due on them. However, if it isn`t your turn to collect that total sum, then you should calculate the sums that you have already paid and pay the Zakat due on them. This is of course if they reached Nisab and one full lunar year elapsed over possessing them, and the same ruling applies to other sums that you own so long as they meet the same conditions. Debt isn`t a valid excuse for not paying the Zakat because of the generality of the texts {Quran & Hadith} about the chapter of Zakat. And Allah knows best.
