"How is GST on flats calculated with abatement for undivided share of land in projects starting after 1.4.2019?"

GST is charged on two thirds amount on under construction flats as per Notification 11/2017- CTR read with explanation thereunder.

If the residential flat is purchased in a project started after 1.4.2019, then GST is payable @ 7.5% on the amounts paid to purchase residential flat on two thirds value of the flat.

That means if flat is purchased for Rs 90 lakhs, GST at 7.5% is payable on Rs 60 lakhs being two thirds value. GST would be Rs 4.5 lakhs even if two thirds abatement is given to GST rate of 7.5%.