Overtime are considered as wages under the ESIC act under Sec.2(22).(Refer : Wages | Employee's State Insurance Corporation, Ministry of Labour & Employment, Government of India)
So you will have to deduct Rs 420 for the gross salary Rs 24000/-
ESIC will be deducted on the full amount of Rs 24000/- as per the usual guidelines of ESIC.
There will be no waiver on the amount as it has increased above Rs 21000/-
E.g : If My salary is Rs 30000/- . Due to certain deductions/absenteeism, loans if my salary becomes Rs 15000/-. I would not be suddenly covered under ESIC.
Similarly for ESIC the normal gross salary of a person is considered for coverage. Salary may increase / decrease each month for employees basis receipt of Overtime. Incentives , Absenteeism. However the stipulated structure ( basic , da,hra , medical , conveyance , special allowance) remains constant.
i.e For a person with a salary of Rs 21000/- or below . If no absenteeism , bonus or overtime is present , then his salary will always remain Rs 21000. So 21000 should be wage decided for coverage.
14th August 2017 From India, Mumbai
14th August 2017 From India, Noida