Can you please tell us your entire procedure for the Performance Appraisal (PA) at your company? Why are you required to write "letter" to the employee? Was PA conducted in front of the respective employee or it was done in their absence?
To bring transparency in the process, Manager conducts PA of his/her junior in front of him, awards the marks and takes signature on the PA form. If the signature is taken, then there is no need for separate letter as such. At the same time development feedback is given on career development. However, it is a different matter.
Writing letter is fine but it only increases the job of the HR Department. HR has myriad other jobs and getting into this kind of clerical work is not advisable.
16th May 2018 From India, Bangalore