GST applicability on single unit

No GST over any property if it is 'ready to occupy' ........ only stamp duty & registration charges levied.

As per the clause 5(b) of the Schedule II of CGST, Act,
2017, construction of a flat / house / complex intended for sale
is a supply of service.
However, if the entire consideration towards the
Flat/House/complex is received after the receipt of
completion/occupancy certificate from the competent authority or
after its first occupation, whichever is earlier, then such
activity is neither a supply goods nor a supply of Service, as
provided under Clause 5 of Schedule-III of CGST Act, 2017.
Accordingly, a transaction involving sale of such immovable
property after initial occupation or after receipt of occupancy
certificate, is a sale of immovable property and it does NOT Attracts GST,. ... BUT ITC has to reverse on Sale of sucb flat , As per the provision of Rule 42