It is believed that the confirmation by HR is verbal, and that you enjoy good rapport and the company is responding to your queries.
In incentive policy usually it is stated that interpretation of the clauses by the management and decision of the management on incentives shall be final.
If possible you may use your resources and obtain a copy of the annual incentive policy. Based on the annual incentive policy you can contest.
Did you remain in the employment for the full period of the annual incentive policy?
You have mentioned there is a separate component called Monthly Performance Pay (MPP) which is given to the Employee along with the Salary. In your offer letter issued to you before joining, or your appointment letter issued to you at the time of joining, is there any or detailed descripttion of MPP. Is MPP part of your CTC?
It is believed MPP is a variable component and based on monthly performance it can vary.
You have mentioned "According to MPP Policy, I have to give back the MPP for 3 months which is also the notice period if I am resigning. This MPP I have already given to them while resigning",
This implies that:
-your notice period is 3 months and in case of resignation without prior notice, you have to tender notice pay.
-You have to and you have paid 3 months MPP. In addition you have to tender notice pay. So in case of resignation with immediate effect you shall pay for 6 months (3months MPP+3 months notice pay)
-MPP is a policy and this policy is applicable to you. Is MPP policy a part of your employment contract? Is MPP policy stated in your appointment letter? Have you accepted it in writing?
The impression is that company likes to pay more to performing employees and wants majority of the employees to be near best level of performance.
The company has enforced an airtight process of collecting MPP and a major chunk of annual incentives, both of which are earned due to highest level of performance, although company is silent on amount to be paid to the departed employee at the time of disbursement of annual incentive. Company should be fair and should state this clearly like they have in many other policies they have enforced.
Company should supply a copy of the annual incentive policy also.
You may represent in writing under receipt, to the good offices of your appointing authority, MD, CEO, Head-HR, Company secretary, and mention that you have always strived to give best of your performance and exerted to earn the payouts and wages expressed in the MPP and annual incentive policy of the company and have earned them with the performance delivered by you.
You may mention that you have given highest priority to your job and responsibilities and cared less for your personal time, and convenience.
You may request their good office to disburse you the 100% of the annual incentive earned by you(if you have worked for period of the annual incentive).