Dear Jossy Justin,
Since you have not mentioned the interval of payment of Incentive therefore, I am producing here the rule that allowances, incentive, profit sharing etc. whatever nomenclature, if being paid on regular monthly basis and Gross up to Rs. 10000/- will be coveable under the Act and Contribution has to be deducted and deposited.
Any allowance, Incentive etc. being paid more than the interval of two months is exempted to consider the wages for E.S.I. contribution.
I would suggest you to check if on adding said incentive with the monthly salary comes out more than 10000/- then show it on wage register on monthly basis, then your employees automatically become exempted from E.S.I. purview, other wise pay it on quarterly basis so that the amount of incentive will be exempted from E.S. I. contribution.
Thanks
Mohd. Arif Khan