What is the ruling on the financial trading system based on benefiting from the client's bank certificate for a period of 10 months in exchange for 20% or more monthly of the total amount, knowing that the principal amount is not touched or deducted from at all?

This contract is usurious and forbidden if the client deposits an amount in the bank for a 20% return on capital monthly. Depositing money in the bank is considered a loan, and interest on it is usury (riba). Lawful investment has three conditions: that the bank invests the money in permissible activities, that the capital is not guaranteed, and that the profit is specified as a common percentage of the profit, not of the capital. Bank deposits for which interest is paid are forbidden usurious loans. As for deposits handed over to banks that adhere to the provisions of Islamic Sharia under an investment contract for a share of the profit, these are Mudarabah capital, and the rulings of Mudarabah apply to them, which include the impermissibility of the bank guaranteeing the Mudarabah capital.