Secondly, when calculating Zakaat, the liabilities are subtracted from one’s assets and Zakaat is payable on the remaining amount if it reaches the Nisaab threshold. However, assuming the loan being a long-term loan, you cannot consider the entire loan as a Zakaat liability to be deducted from your Zakaatable assets. In such a case, some Ulama hold the view that the person may only deduct the instalment of the month in which his Zakaat becomes due. Other Ulama grant leeway of deducting a full year’s instalments as a Zakaat liability. In both views, there is no leeway of deducting the entire loan as a liability because the entire loan is not a current liability as its payment stretches over a lengthy period.
Therefore, it is best that you only subtract the instalment of one month and thereafter you should determine whether the remainder reaches Nisaab or not; if it does, then Zakaat will be incumbent on the cash etc.