What is the ruling on the additional percentage (10%) that the intermediary takes monthly from the profits before dividing them among the investors, knowing that they consent to it, and is it permissible for the intermediary to take another percentage for himself with the knowledge and consent of all parties?

Brokerage is permissible, and it is permissible to take a fee for it, provided that the fee is known. However, a fee stipulated for the broker as a percentage of the profit is not permissible due to the ambiguity (جهالة) and uncertainty (غرر) involved. Consequently, the contract becomes invalid, and the broker is entitled to a wage equivalent to their services (أجر المثل). It must also be noted that intermediation is not permissible in the sale of shares of companies that operate in forbidden fields, or promote forbidden matters, or deal with usurious banks.