Human Resouce Management

Hello there,
I am working in a big construction company as a HR and Administrator. The organisation had no a defined management for the last 16 years and i am here to establish one with a a help from the employees. I have so many challenges. . . (leave that aside for now anyway)
I am writting to ask, what do we call a letter given to an employee who left the job for another job somewhere else (accomplished his/her contract and do not want to renew) or for other known and genuine reasons? Like, Ms so and so has been working with us since 1999 to 2001 as a machine operator etc. etc
I have been asked to write to ex-worker but realy do not know how to call that kind of letter, moreover i am not sure if the sample/format i use is correct.
Please, someone help me with the name and format, Pleeeeeeease!

Hi ,
I guess the word you are looking for is an "Experience Letter". This is given to an employee on the completion of the employement period/ tenure in a particular Organisation.
The details which should be included are:
1) Full Name of the Employee
2) Employee Id: (If applicable)
3) Last Designation held
4) Date of Joining
5) Last Date of working
6) Reason for Leaving
7)Pleasentaries & Closing
This letter needs to be printed on the Company letterhead and duly signed and stamped by a competent authority. Generally it would be the Head of the HR in the Organisation or the Director/MD/ Head of the Organisation.
This letter is released with the FnF (Full and Final settlement) of the employee dues.
Thanks