GST exemption on development rights and lease premiums for residential projects, with reverse charge tax for unbooked apartments. Amendment grants GST exemption for transfer of development rights (TDR)/FSI and upfront lease amounts used for construction of residential apartments intended for sale, with the exempt amount pro rata based on carpet area of residential apartments relative to total carpet area. Promoters must pay tax on the proportion attributable to apartments remaining un booked at completion/first occupation on a reverse charge basis, calculated by applying the carpet area ratio to the GST otherwise payable, subject to capped tax percentages for affordable and other residential apartments. Deemed valuation rules and defined terms are prescribed.