Ruling on working on a program that enables company clients to trade in shares
Question

                I was offered to work as a programmer in company of investment and dealing in the stock market, to design computer programs that make buying and selling shares easier in the market for the favour of my company’s clients. Is it permissible islamically to do this, knowing that some of the companies in the bourse are involved in haram activities, some use banks mortgages, and some are just of halal activities? 

I do not or sell shares myself. I just make this process of buying and selling easier for my company’s clients. Is this considered co-operation in sin and transgression, if a client buys shares of a company involved in haram activities using my program? Or the sin is on the client himself if he does so? The company I work for told me that they do not buy or sell shares of companies whose activities are haram. Shall I accept this offer until I make sure myself if they were truthful about this or not?.
Praise be to Allah.
    If the company deals only in permissible shares, then there 
    is nothing wrong with working on a program that enables clients to buy and 
    sell these shares via the stock exchange. But if it deals in both haraam and 
    permissible shares, it is not permissible to help with that, by programming 
    or otherwise, because it comes under the heading of cooperating in sin and 
    transgression, and Allaah says (interpretation of the meaning): 

    “Help you one another in Al‑Birr and At‑Taqwa (virtue, 
    righteousness and piety); but do not help one another in sin and 
    transgression. And fear Allaah. Verily, Allaah is Severe in punishment”

    [al-Maa’idah 5:2]

    Sin is not limited to the one who deals directly with the 
    haraam thing, rather it also affects the one who helps him with that, 
    approves of it or promotes it. 

    Based on this, if you are certain that the company only deals 
    in permissible shares, then there is nothing wrong with you accepting a job 
    with them. 

    We ask Allaah to guide you. 

    And Allaah knows best.