When an employee receives a promotion, it's typically announced in a job promotion letter. This is a formal communication between the company and the employee being promoted, briefly acknowledging the new role and outlining its place in the reporting structure.
It's also a chance for the employer, via their representative in human resources, to offer congratulations to an employee who has grown along with the organization. Here is a template of a promotion offer mail:
Dear [employee name],
Congratulations on your promotion to the position of [designation of new position] effective [date], 20XX. We are confident that you will continue to demonstrate impact in your higher responsibility.
You will report to [Director name]. She/He is looking forward to working with you as you transition into your new role at [Company Name].
Consequent to your promotion, we have revised your compensation to [New CTC]. This will be effective from [Effective date]. Please find attached a copy of your increment letter.
Again, congratulations on the new position and best wishes as you embark on higher responsibilities. I am sure you will make the best of this opportunity for your professional growth at [Company Name].