The notice period of 90dasy may not necessarily be applicable in your case.
The stand of employer that ‘or a payment in lieu of notice period, if permitted by the Firm’ may not necessarily be tenable in your case.
The contentions of employer may not necessarily be legally tenable.
While posting such queries employee should post basic information!
What is this establishment; Commercial, Industrial?
What is its nature of business say; IT, ITeS?
How many persons are employed in it?
What is your designation and nature of duties?
How many persons report to you?
Do you have any power to sanction leave/increment/appoint/terminate/appraise etc etc ?
You are in which state? Since how many months you are working? Are you under probation period or your service is confirmed in writing?
Do standing orders (model/certified) apply to establishment and your designation?
What is notice period as per appointment letter/offer letter and what was notice period tendered by you?
Was ever any stinker, memo, show cause notice on any misconduct issued to you?
Does the establishment have its appraisal system? Do you have copy of signed appraisal forms, matrix, KRA’s, performance date? How was your performance?
Are you a member of employee’s/trade unions?
Do you have evidence of all tasks are completed and nothing is pending at your end?
Has the establishment issued/supplied, offer letter, appointment letter, salary slips of all months, PF number and a/c slips of all years, ESIC card, correct FnF statement, Form 16 as per correct FnF statement, acknowledgment and acceptance of notice of resignation/final resignation, acknowledgment of handover of charge, NOC/NDC……………?