All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
The loan that you took has entered into your possession from the day that you borrowed it, and you are responsible for paying it back, so if a whole lunar year elapses on it while it is in your possession and it reached the nisaab (minimum amount liable for zakah), then you are obliged to pay zakah on it in principle. If you did not repay the debt, as you clarified in the question, then should you deduct the debt that you owe from the money that you possess and then pay zakah on the remaining amount or not? The majority of the scholars believe that the debt is dropped from zakah of hidden money, i.e. cash money and tradable items. Their evidence is what was proven from ‘Uthmaan ; that he said in the presence of some Companions: "This month is the month when you should pay zakah, so whoever has debts should repay it and then pay zakah on the remaining amount of money; this was reported by Maalik and Ibn Abi Shaybah and others."
Also, if we say that the indebted person has to pay zakah, then this means that zakah would be paid twice on the same amount because the creditor has also to pay the zakah on his money [which he lent], as is known.
Ash-Shaafi’i holds the view in his new opinion that debt does not exempt a person from paying the zakah; the prominent scholars Ibn Baaz and Ibn ‘Uthaymeen chose this opinion; their evidence is the general saying of Allaah (which means): {Take [O, Muhammad] from their wealth a charity by which you purify them and cause them increase.} [Quran 9:103]
Also, the Prophet used to send his workers to collect alms, and they did not use to ask the people whether or not they had debts. Shaykh Ibn Uthaymeen answered about the saying of ‘Uthmaan, "It proves that if the debt is immediate and the debtor wants to repay it, then he puts it in priority over the zakah [i.e. he first repays the debt]; as regards the debts that are not immediate, then this does not prevent from paying the zakah on it. This is the saying that a person should follow in order to be on the safe side."
The view that we adopt here in Islamweb in regard to this issue is the view of Imaam Maalik which is that the debt is deducted from the wealth on which one is obliged to pay zakah, unless one has other funds that are not zakatable and are in surplus of his need, then he should consider it instead of the debts and then pay the zakah on the wealth that he has.
Based on that, if you have tradable items, such as homes, cars, or furniture that are in surplus of your need, then you should consider this against the debts, so you pay zakah on the money that you borrowed. In any case, it is better to pay the zakah on your debt in order to be on the safe side as per the new opinion of Imaam Ash-Shaafi’i, or that you only deduct the immediate portion of debt that you have to repay, as per the view chosen by some scholars.
For more benefit, please refer to fatwa 116828.
Allaah knows best.