He has some money in a bank account from which he pays his monthly expenses – does he have to pay zakaah on it?
Question

                He has some money in the bank for which one year has passed and it is not in a savings account; he pays household expenses from it every month as well as water and electricity bills. Does he have to pay zakaah on it or not?.
Praise be to Allah.If the 
    amount of money reaches the minimum threshold (nisaab) – which is the 
    equivalent of 85 grams of gold or 595 grams of silver – and a full hijri 
    year has passed since acquiring it, then zakaah must be paid on it, even if 
    something is taken from it each month, because of the general meaning of the 
    evidence that zakaah must be paid on wealth that is subject to zakaah, when 
    one year has passed. 
If we assume 
    that this money reached the nisaab at the beginning of the year, then it 
    fell below the nisaab during the year, no zakaah is due on it, and the 
    reckoning of a new year should begin when it reaches the nisaab again. 
For example: 
    if the amount of money reaches the nisaab in Ramadaan, then it falls below 
    the nisaab in Dhu’l-Hijjah, then you acquire more money which brings it back 
    up to the nisaab in Rabee’, then you should start reckoning a new year from 
    Rabee’. 
Al-Nawawi 
    (may Allaah have mercy on him) said: Our view and that of Maalik, Ahmad and 
    the majority is that is in order for zakaah to be obligatory on wealth that 
    is subject to zakaah and for which one year must have passed, such as gold, 
    silver and livestock, the nisaab should have been present throughout the 
    year. If it falls below the nisaab for a moment during the year, the year is 
    cancelled out, and if it reaches the nisaab again after that, a new year 
    should be calculated from the moment when the nisaab was reached again. End 
    quote. 

    Al-Majmoo’ (5/506) 
And Allaah knows 
    best.