Is it permissible to pay the Zakat on behalf of a deceased father who had not paid his Zakat, and how is Zakat to be paid on money that includes a large amount of bank interest, knowing the desperate need for this money?

The heirs must pay the Zakat for the years they are certain their father did not pay it during his lifetime, because Zakat is a right of the poor and a debt that does not lapse. It must be paid before the division of the inheritance. If the number of years is unknown, Zakat should be paid for the amount that is certain, and it is preferable to be cautious if all heirs are willing to donate. After paying the Zakat, the wealth is divided among the heirs, and each heir pays Zakat on their share after a full year has passed. It should be noted that if the money is deposited in a usurious bank, Zakat is obligatory only on the principal amount deposited and not on the usurious interest. Rather, the usurious interest must be disposed of by spending it on public welfare.