Is it permissible for an accountant to take a commission on booking travel tickets for workers without their knowledge?

It is permissible for your friend to take a commission for booking tickets for workers if this is not part of his work for the company, provided the company gives permission if he uses work hours or company equipment. It is not permissible to take a commission from the workers without their knowledge, as this is consuming wealth unlawfully and is an injustice. However, if the booking is not part of his job, he may agree with them on a fee for this service.