Is zakat due on the principal of an investment deposit, and what is the difference between zakat on a bank deposit, an investment deposit with a return, and an investment deposit based on Mudarabah? What is the benefit of depositing money for investment Mudarabah if zakat is due on the principal, and is there a difference between zakat on money and zakat on cash?

A guaranteed bank deposit in an interest-based bank, in exchange for profit, is not permissible. Rather, it must be withdrawn, and all the profit must be disposed of by spending it on charitable causes. As for an investment deposit in an Islamic bank, which is a mudarabah (profit-sharing partnership), there is no objection to it, and zakat is obligatory on both its principal and its profit. In any case, zakat is obligatory on a deposit whenever it reaches the nisab (minimum threshold) and a hawl (one lunar year) passes over it, whether it is permissible or impermissible. This is contrary to some fatwas that analogize it to land; rather, it is like the two currencies (gold and silver), and zakat is obligatory on it.