How should I convince the management about the importance of an appointment letter to an employer?

Hello Everyone, I have recently joined a company as an HR, before me there was no HR in the company only a legal adviser is theirs. They don't provide an Appointment letter to any of employee when I joined every employee want me to give them an appointment letter, how should I convince the management about the importance of an appointment letter to an employer?

The appointment letter plays very important role to protect the interest of both employer and employee in the eyes of law. There are many court rulings to support your request.
Make an effective presentation to your top management about the need to introduce the practice of issuing appointment letter

Appointment letter is nothing but an employment contract, which has a legal bearing.
If you are hiring the services of any person, an employment contract is to be entered into between that person and you (Employer). When a person is joining, his designation, remuneration, place of posting, probation, confirmation, clause on separation, other terms and conditions, etc. are to be conveyed to him through an appointment letter only. Similarly if an employee is relieved, he should be given a Service certificate also.
Hence you may convince your management accordingly. If you are employing people without
issuing Appointment letter, this may lead to far reaching consequences at a later date.