Praise be to Allah.
It is not permissible to give the representative any money or gifts, because that comes under the heading of bribery and haraam gifts to workers. He is employed by his company and buying the goods is part of his work for which he is paid a salary; he is acting on behalf of his company when he makes purchases, and any profit or discount that he gets should go back to the company, and it is not permissible for him to take anything of it.
Ahmad and al-Bayhaqi narrated that the Prophet (blessings and peace of Allaah be upon him) said: “Gifts to workers are ghulool (lit. stolen war booty),” meaning a betrayal. The hadeeth was classed as saheeh by al-Albaani in Saheeh al-Jaami’, no. 7021.
“Workers” means employees, so everything that comes to the employee because of his work is a kind of betrayal and haraam.
Al-Bukhaari (7174) and Muslim (1832) narrated that Humayd al-Saa’idi (may Allaah be pleased with him) said: The Messenger of Allaah (blessings and peace of Allaah be upon him) appointed a man from al-Asad who was called Ibn al-Lutbiyyah. When he came he said: This is for you, and this was given to me. The Messenger of Allaah (blessings and peace of Allaah be upon him) stood up on the minbar and praised and glorified Allaah, and said: “What is the matter with an agent whom I send, and he says, ‘This is for you and this was given to me’? Why doesn’t he sit in the house of his father or the house of his mother and see if he is given anything or not. By the One in Whose hand is the soul of Muhammad, no one of you gets anything from it (unlawfully), but he will bring it on the Day of Resurrection, carrying it on his shoulders, even if it is a groaning camel, a lowing cow or a bleating sheep.” Then he raised his arms until we saw the whiteness of his armpits, then he said: “O Allaah, have I conveyed (the message)?” three times.
It may be said here: if this representative sat in his house, he would not be given anything; he is only being given something so that he will buy from you for his company. This may make the employee betray the trust, so he buys from the one who gives him things, even if that which others have is better and more suitable. Hence sharee’ah closes this door. So no gifts should be given to the worker, and nothing should be given to him.
It is very unfortunate that these bribes are widespread nowadays, and people have come up with various kinds of them, even adding to them deceit and lies, so the seller writes a false price for the representative, and a fabricated invoice, to help him betray the trust and acquire haraam earnings, so that he will buy from him again. What we should do is beware of all things that come under the heading of bribery and haraam gifts for workers.
And Allaah knows best.