Regarding guidelines on service tax

Dear Sir, I am working in Railway and we are awarding cleanliness contract which are mainly labour oriented contracts. In such type of contracts service tax is an statutory component which is to be calculated on labour component. As concern to labour component it includes following three parts :- (i) Minimum wages applicable as notified by Govt. (ii) ESI (Employess State Insurance) (iii) EPF ( Employees Provident Fund) There are following two concepts for calculating service tax on labour component :- (a) In some departments service on labour component is being calculated on the sum of Minimum wages and ESI only and EPF is not counted as EPF amount is refundable amount. (b) Whereas in some departments service tax is calculated on sum of minimum wages, ESI & EPF. I want to know what is exact rule for calculation of service whether it will calculated on sum of minimum wages & ESI only or on the sum of minimum wages, ESI & EPF. If there is any circular of concerned ministry on the matter the same may please be also quoted. Regards Devi Lal