Is the money my relative receives from a company where employees bribe customers to sell products at cheap prices lawful or unlawful?

The scholars are unanimous in their prohibition of bribery, both taking and giving, considering it one of the major sins. "The Messenger of Allah (peace be upon him) cursed the briber and the bribed."

Your relative must advise the employees and remind them to fear Allah, clarify the prohibition of bribery, and explain that consuming unlawful wealth is a reason for prayers and good deeds not being accepted. The Prophet (peace be upon him) said: "O people, Allah is Good and accepts only good... A man whose food is unlawful, whose drink is unlawful, whose clothing is unlawful, and who is nourished with unlawful things, how can his supplication be answered?"

And he (peace be upon him) said: "Every body that is nourished by unlawful earnings, the Fire is more befitting for it."

If they do not respond, he must inform the company owner or whoever has authority.

If your relative's work does not involve these prohibited transactions and he performs his duty without deception or favoritism, then there is no objection to him working in the company. He is not harmed by the disobedience of others after he has fulfilled his duty of advising.

However, if he knows that his work will lead him to engage in bribery, or assist in it, or accept it, and neglect to condemn it when he is able to, then it is not permissible for him to remain in the company.