This is an additional amount that is given to employees for their overtime hours. Mostly, it is the half time in time and one off. 

Overtime premium is paid to the workers for the extra time worked than the normal working hours specified in the Factories Act, 1948 or work agreement with the union. The extra time is paid at a higher rate than the normal time rate, for example, if a worker works beyond 8 hours in a day or 48 hours in a week, he is paid with double the wages for the extra time worked.