Dear Suresh K,
Components of Salary
There are two parts to the salary: a) Daily Salary, i.e., basic and all allowances, and b) Reimbursement. Though washing allowance, conveyance allowance, etc., are paid in the monthly salary, they are considered reimbursements. If an employee is not issued a uniform and there is a transport facility, then you have to deduct the ESI contribution.
Night Shift Allowance
As per my knowledge, in many companies, they have second and third shift allowances, and companies are liable to deduct ESI contribution because it is an allowance that is paid in their monthly salary.
Regards,
Clement