Is it permissible for an Islamic bank to purchase goods from its clients after selling them to them, and is it permissible for it to deduct a year's profit in advance upon signing the contract, along with deducting only the principal amount in the first year?

The question contains two points:

First: It is not permissible for one of the bank's departments to purchase the commodity from the ordering party after the contract is finalized if that department is affiliated with the bank and they share the same financial liability, because the bank is a single legal entity. This falls under the category of inah sale (buy-back sale), which ultimately leads to a form of usury (riba).

Second: It is permissible for the bank to take an upfront installment of the price after signing the sale contract, even if the installment equals a year's profit. The decisive factor is what the two parties agree upon regarding the method of installment payments.