If someone passes away not leaving enough behind to pay off his debts, is it permissible for someone else to pay the debt using zakat money?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
The Messenger of Allah said: "The believer's soul is suspended by his debt until it is settled for him."
No one is responsible to pay the debt on behalf of the deceased. If the deceased left behind wealth, then the debt should be paid from it before dividing the estate. If the entire estate is used and still there are outstanding debts, then none of the inheritors are obliged to pay. Yes, if they do so on their own accord, in the hope that the deceased is not punished, they will be rewarded and that will be a kind gesture on their part. However, they cannot be compelled to do so.
In regards to your query, it is not permissible to pay the debt of the deceased using the money of zakat according to the Hanafi school of Islamic Fiqh.
Therefore, if someone desired to pay the debt of a loved one who has passed away with other than zakat money, this will be permissible.
Only Allah knows best
Written by Maulana Muqtaur Rahman
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham