Is it permissible to join an employee savings program whereby a percentage of the salary is deducted in exchange for the employee later receiving several basic salaries, knowing that the bank invests these deducted amounts?

It is permissible to work in the Islamic branches of the aforementioned bank, but it is forbidden to work in its usurious branches. The money deducted from the employee for investment takes the ruling of Mudarabah (profit-sharing). For a Mudarabah to be valid, the share of both the capital and the Mudarib (investing partner) must be a common percentage of the profit, not a fixed amount. Furthermore, the capital must not be guaranteed by the worker unless there is transgression or negligence. Also, the Mudarabah must be in something permissible according to Sharia. The bank's payment of specific amounts to the employee shifts the transaction from Mudarabah to a forbidden usurious loan. What further complicates the matter is the unknown nature of the investment field for these amounts.