Dad Died Before Paying Zakah: What Should We Do?
QMy father passed away, but unfortunately he did not pay zakah for a reason or another. Should we as his heirs pay the zakah that was due on my father?
ANSWER
Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.

In the Name of Allah, Most Gracious, Most Merciful. 

All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.

In this fatwa:

If the zakah was due on your father before he died, the amount of zakah for that year becomes due on him and the heirs must pay it like other debts to other persons.

In his response to your question, Prof. Dr. Monzer Kahf, Professor of Islamic Finance and Economics at Qatar Faculty of Islamic Studies, states:

If the hawl is due, i.e., the zakah is due on your father before he died, the amount of zakah for that year becomes due on him. In this case, the heirs must pay it like other debts to other persons.

Some scholars even argue that the debt of Allah is stronger in the requirement to be paid than the debts to people.

Also there are scholars who say that now the property belongs to heirs and they are not responsible for the neglect of the deceased. Well, it is true technically! But he is your father and even if you make sadaqah on his behalf, he will be rewarded for it. Zakah is definitely more important.

Allah Almighty knows best.