Is it permissible to buy shares in a company that sells halal products, if the company sells its shares to employees at a reduced price (20% margin), and it is stipulated that they must be held for three years, knowing that the company deals with usury only to a very small extent (less than 1%) and does not borrow from banks?

It is permissible to buy company shares and benefit from their incentives if the company sells permissible goods, does not borrow with interest, and does not deposit its money in interest-bearing accounts. The establishment of a joint-stock company with permissible objectives and activities is religiously permissible, whereas it is forbidden to contribute to companies whose primary purpose is prohibited. It is not permissible to buy shares in companies or banks that engage in some interest-bearing transactions, or manufacture or trade in prohibited items. As for interest less than 1%, you must dispose of it, because gifts from current accounts are forbidden.