How is zakah paid on money that increases monthly?

Question:
The questioner says: By the grace of Allah, I have reached the nisab for zakah, and every month another salary comes in. How do I pay the zakah on this money? May Allah reward you with good.

Answer:
This is the case of someone who saves money every month from his salary or from income that comes to him every month. It is difficult for him if he wants to determine the time for each amount separately; it burdens him and he cannot keep track of it. But the best option, and the one on which the fatwa is based, is that he designates a month of the year.
That month becomes the time for paying his zakah. So when that month comes, for example Ramadan, he pays zakah on what has accumulated with him that has completed its hawl, and on what has not completed its hawl until the corresponding month of the following year. Yes, this provides caution and ease for the person, and by this method he is certain that he has paid the zakah in full. Yes.