All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Paying a commission to an employee in a company in return for giving the work order to you is not permissible because that employee is an agent for his company and he gets a salary for doing his job, so it is not permissible for him to take a commission for it without the permission of his employer. Therefore, it is forbidden to give a commission to him because that constitutes Ghulool (unlawful earnings). It has been proven that the Prophet used a man from (the tribe of) Al-Azd to collect zakah and charity, and when he returned, he said, “This is for you, and this was gifted to me.” Thereupon, the Prophet said, “Why hadn't he stayed in his father's or mother's house to see whether he would be given presents or not?” [Al-Bukhari]
This hadeeth is clear evidence that the gifts that are given to the employee to complete his work for which he gets a salary are forbidden.
An-Nawawi said, “This hadeeth clarifies that the gifts received (by workers or employees) for doing a job are forbidden.”
Moreover, Abu Daawood reported that Buraydah narrated that the Prophet said, “If we employ someone to do a given work and we pay him for doing the work, then whatever he takes after that (because of doing the work) is Ghulool (unlawful earnings).”
Allaah knows best.