What is the ruling on money acquired from a brokerage deal, when it became clear that the seller operates informally or obtains goods from warehouses through illicit means (such as theft), and how can one absolve oneself of this money given the impossibility of returning it to the parent company?

Intermediating between a buyer and a seller (brokerage) is permissible, and the agreed-upon fee is deserved after the completion of the sale. If you were unaware that the sale was invalid (such as selling something the seller does not own) until the contract was concluded, then your fee is lawful, and donating it as an act of piety is good. However, if you knew of the invalidity of the sale before or during the contract, then you do not deserve a fee. If you received a monetary fee, return it to the one from whom you took it. If that is not possible, spend it on the welfare of Muslims. If the fee was a part of the merchandise, return it to the company, or its value if you have disposed of it. The buyer must return the item to its owner and reclaim its price, and the seller must return what he sold to the company because it is not his property.