GST On Advance related to Real Estate

Arup Ghosh (48 Points)

07 June 2017  
I am from Real Estate Organization my query is
If a buyer pay Rs.500000(inc service tax) as advance on Flat against the future instalment in May accordingly we have paid the service tax in June and raise a advance bill on that amount but the actual Event completion against the advance in the month of July 17. In that case is we required to collect the difference tax from Buyer i.e GST 7.5%(12 - 4.5) ?