What is the ruling on subscribing to "Petrochem" after the subscription has already taken place?

The question should be asked before acting. We cannot judge the company in question because we have not reviewed its system. Its regulations must be examined to determine the extent of its adherence to Sharia (definition) guidelines. If the company engages in permissible commercial activity, then it is permissible to subscribe to it and trade its shares, provided that it does not deposit its funds or invest them in usurious banks. Otherwise, it is not permissible to trade its shares, for Allah Almighty says: "And do not cooperate in sin and aggression."