Need expert advise in service tax

Gaurav Mahajan (Articled Assistent (CA Final))   (39 Points)

04 January 2008  

X  Ltd is in the business of selling & erecting towers for its telecome customers.This Co. Purchase towers from  A. Ltd which delivered the towers at the site as per customer's (telecome co.) choice. A. Ltd is charging Freight from X Ltd. including the Am. of Service tax on transport. 

X Ltd is charging its customer, Freight with certain amount of margin .

Will that margin is taxable under service tax as business support services or by any other means ?

Plz mention the relevant section/circular.