Is zakat due for each of the five years I have participated in the society, or is it due after the full amount has been completed and received?

For the amount contributed to the association, two conditions must be met for zakat to be obligatory: reaching the nisab and the passing of a complete lunar year (hawl) upon it. The nisab is equivalent to 85 grams of gold or 595 grams of silver. If both conditions are met, the participant must pay zakat on each installment when its hawl is completed, at a rate of a quarter of a tenth (2.5%). If zakat was not paid on past installments, then it must be paid for each past year, provided that each installment, either by itself or when combined with others, reached the nisab.