The service tax is always leviable on the value of service provided and not on the value of goods. In case of restaurant service also service tax is leviable on the value of service. However if the service charge and food cost is not seprately identifiable then there is a provision to charge service tax on 30% of the value of bill. The bill amount will include the cost of food and the cost of service. this 70% abatement is given to exclude the value of food.