From the Govt. Circular dated July 2010, there is sufficient clarity that:
Payments received by a Builder of a Residential Complex from the Purchaser on and from 1st July, 2010 onwards is subject to Service Tax.
All payments made to the Builder by the Purchaser, before 1st July 2010, is exempt from Service Tax.
No Service Tax is applicable (irrespective of date of Payment), when the Purchase is made AFTER the issuance of the ‘Completion Certificate’ of the Residential Complex.