Is it permissible for an employee to take a commission from the company's clients, or to profit from his job without harming the company?

The commission paid by dealers to company employees is not permissible except with the company's permission, because it falls under the ruling of forbidden gifts to workers, as was established from the Prophet, peace and blessings be upon him, in the story of Ibn al-Lutbiyyah. However, if the company permits it, there is no harm in it, provided that it does not lead to a violation of Islamic law.