ESIC calculation changes for contribution including over time?

Dear, If any employee gross is 19000, and after OT it become 22000 then should employer pay his contribution in ESIC whether it is on 19000 or 22000 or 21000 or not?
Pls advise.
Regards

ESI eligibility should be on Fixed gross. If the employee fixed gross is not greater than Rs.21000 you should pay the esi contribution for earned gross of the respective month. Whether it is 19000 or 22000 or 21000 or 30000 you should pay the actual earned gross because OT will attract ESI.

Mam
If my fixed gross is 19000 and OT is 3000 then
how calculation will be done,pls advise

ESI contribution should be deducted om gross wages viz. normal wages + OT wages.

If Gross and OT amount exceed ceiling limit of 21000/- ,then should we pay contribution ?
Sometime Gross and OT below 21000/- also

ESI to be deducted during contribution period. e.g. Gross Salary for the purpose of ESI as on 01.04.17 is Rs. 19000/-, ESI would be deducted on Rs. 19,000/-,
In May-17, He gets OT of Rs.2500/-, Now Salary is Rs. 19,000/-+Rs. 2500/- = Rs. 21,500/- and ESI would be deducted on Rs. 21,500/-.(Not on Rs. 19K or 21K)
In September-17, His Salary is increased to Rs. 23,000/-. (Assuming no change in limit) From the next contribution period, He won't be member of ESIC, But in current contribution period ESI would be kept deducted. Thanks.