The zakah on a current account that increases and decreases during the year

Question:
We are still with our brothers and sisters in the Wednesday gathering and the live fatwas. Umm Layan from al-Qasim says: Shaykh, if there is one hundred thousand riyals in my current account at the bank, it may increase during the year to one hundred and fifty thousand riyals, and it may decrease during the year to eighty thousand riyals. When the lunar year is complete, I request a statement from the bank for the year in which the zakah is due, and I look at the lowest amount the account reached, which is eighty thousand riyals, and I pay the zakah on that, because it is the amount on which the year has certainly completed. Is my action correct?

Answer:
Yes, this is what is obligatory. The Muslim must pay zakah on the amount on which the lunar year has completed and which reaches the nisab. Whatever decreased before the completion of the year, there is nothing due on it. Yes.