I work in big engineering organization. I have a very efficient, dutiful and experienced supervisor working under me. He has gained a great respect for his longtime services in the organization. By virtue of his experience and knowledge, he is important for our organization.
A few days ago I learned of a few complaints against him
He claims overtime for more hours than he has actually done.
He accepts delivery of substandard items from some vendors in return for financial benefit.
He promotes favoritism among our staff, giving unauthorized benefits to some workers including extra leave, overtime etc.
Considering his services and the mandatory requirements for our organization, I decided not to take disciplinary action against him. At the same time, I want to communicate to him that he should not dare to repeat such practices in the future. By virtue of his experience, age & services, I don't want to tell him personally by calling him in my office.
How can I address this issue effectively and in the best interest of the organization? I cannot afford to expel him from our team, and at the same time I do not want him to repeat these bad practices in the future.