Dear Yasser
Please note that
1. an employee is not covered under ESI if his Gross Salary (Excluding Overtime) is more than Rs. 15000/-. However for contribution the Gross Salary including Overtime is to be considered even if it goes above Rs. 15000/-.
2. Employee if covered at the start of Contribution period that is in April & October remains covered under ESI for the entire contribution period even if the employee cross the limit of Rs. 15000/- during the contribution period.
Hope the input from the group members and this post helps.