Employee Performance - Do we need to issue letters along with mail telling them their performance issue?

Dear All,
I am working with an IT company in Pune. We have recently completed the performance appraisal process. In that, we found that many of the people are not able to justify their work as per the expected level. So we want to take some action as we feel that they are not good enough to keep with the company in the long term as their performance is not that good. For some of them, we have already given a performance improvement plan but overall improvement is not as expected. Some of them are seniors with 4+ years of experience.
So can you pls suggest what action we should take so that they leave the company on their own? Do we need to issue letters along with mail telling them their performance issue?
Kindly suggest how to tackle this situation and improve organizational productivity.

Dear Sunil,
When an employee was put on Performance Improvement Plan (PIM), you should have given him/her official letter stating why it was done and what would be the consequences if after PIP also he/she fails to improve the performance.
Those who were under PIP and whose performance was not improved, for them issue the show cause notice. If the reply is not satisfactory, given them some three months time along with the warning letter and if the performance is still not satisfactory, tell them to put in their papers.
Ok...
Dinesh V Divekar

Dear Mr. Dinesh Divekar,
Thanks for your input.
In my company we gave the PIP for particular duration depending on the output we take the action.
During PIP their performance was satisfactory so we have not got any chance to take action.
But after 2 months we r facing the same performance issue. So we are thinking to give them Notice clearly mentioning that we are giving them last 2 months which is actually a notice from company.
So notice last day is going to be their last day with company.
If we ask them to leave immediately then we have to pay them 2 months notice pay. So in this case we will at least get some time to recruit new people.

Hi all,
I am in construction company as a HR. want to design appraisal rating form, letter and all related to it. can any one suggest about the same ???

Respected all
i am working in auto mob company. i faced a problem regarding the PMS . That workmens are not agree to perform the work and give the output as per requirement and plan . For it we have given training to recover the gap and counselling and motivate them so that we achieve the target . bt after some time we face the same problem . we don't want to issue any official latter for it . so please suggest me the other method which can use and maintain the PMS in the company and achieve the target .
Best regards
Naveen Kumar phougat

Sir,
Be careful before issuing any notice to an employee.
The Govt. is planning to bring IT companies under INDUSTRIAL EMPLOYMENT(STANDING ORDERS)ACT.
Therefore for any notice you issue or any action you take should be technically correct i.e. fool proof.
Go thru the Act and only then take action.
Regards.