It is not half yearly return but contribution period. That means, an employee whose salary (ESI qualifying salary without considering unusual variable pay, like incentives, Overtime pay, and other amounts like washing allowance which are excluded from wages) crosses the limit (at present Rs 15000) in the middle of the contribution period (we have two contribution periods, viz, April to September and October to March of the following year) we have to contribute till the end of the end of the contribution period. That is, if salary crosses Rs 15000 in June, contribution should be paid till September and if in the month of October salary is increased then contribution should be paid till March, ie, end of the contribution period.
Salary of coverage should only be taken as salary for out of coverage. If salary increase is due to increase in any variable component in any month, that should not be taken as increase for the purpose of out of coverage. Variables which are paid in an interval of not more than 2 months should be taken as part of salary whereas overtime will qualify for contribution though for deciding coverage the same is not taken in to account.
Regards,
Madhu.T.K