Renewal of appointment letters? Why?
Letters communicating the revised salary are normally in practice, but the appointment letter, being a contract of employment, will not be renewed across the company. This is because changing the clauses of the appointment letter will involve changes in the conditions of service. In respect of employees who do not have managerial functions, this would attract a violation of section 9A of the Industrial Disputes Act. Therefore, due care should be taken while changing the appointment order. At the same time, if you wish to make amendments, the same can be made by means of a notice with a copy marked to the Labor Officer concerned.
Regarding annexure to the revision letters
I would say that if the employee is not convinced of any component of salary, the conditions for its earning, certainly, the HR has to explain it. After all, it is the duty of the HR to take care of the grievances, make the employee know the matters connected with the employment in the language that is acceptable to him.