GST on advance received for under construction property

Dilip Bhandarkar (Student) (55 Points)

04 March 2021  
A buyer has paid an advance of ₹10 lakhs for a commercial property which is under construction. Sale deed will be made for ₹25 lakhs after the completion.

My queries-
1) Is GST applicable on the advance amount of ₹10Lakhs or the whole ₹25Lakhs?

2) If GST is applicable only on advance of ₹10Lakhs since remaining ₹15 lakhs is received after completion, how to show it in the returns?

thanks in advance.