ANSWER:

If the amount is saved for one lunar year and the amount reaches the nissab then you have to pay the zakat on the full amount. If this is a conventional bank, this is clear riba and it is one of the 7 major sins in islam. 

I have a fixed deposit in the bank which is matuaring in 1 year. Do I have to pay Zakath on it. The profit is shared only at the maturing time I.e. 1 year