Is there Zakah (obligatory charity) due on the money
deposited in a bank? It should be known that some of the money has not completed a Hawl (one lunar year calculated from the time a property reaches the minimum amount upon which Zakah is due), since every month I add a sum of money.
It is obligatory to pay Zakah on the money deposited in a bank when it reaches Nisab (the minimum amount on which Zakah is due) and a Hawl has passed on it, where one should give 2.5% of it as Zakah. If you add a sum of money every month to the original sum, Zakah becomes due on the new sum when a Hawl passes on depositing it, and you should then pay Zakah on the total sum of both the original sum and the new one. If you cannot calculate this exactly, then to be on the safe side, Zakah should be paid on all the money that you deposited, earlier or later, in the bank, in order to discharge your responsibility. You should also appoint a certain time for paying the Zakah due on you, such as the month of Ramadan, lest you should be confused regarding the completion of the Hawl on the money deposited at different times.