GST exemption for development rights and lease premiums with promoter reverse charge for unbooked residential units at completion. The notification exempts GST on services by way of transfer of development rights or FSI and on upfront amounts for long term leases used for construction of residential apartments, apportioned by carpet area between residential and commercial components. Promoters must pay tax on a reverse charge basis for proportions attributable to residential apartments that remain un booked at completion or first occupation, with liability timed to completion/first occupation and subject to capped percentages for affordable and other residential apartments. Deemed valuation rules and defined terms are prescribed.