GST exemption on development rights and lease premium for residential projects; promoter reverse-charge for un-booked units with capped liability. The notification adds nil-rated entries for GST on transfer of development rights/FSI and on upfront premiums for long-term land leases used for construction of residential apartments, with exemption apportioned by carpet area. Promoters must pay tax on the proportion attributable to residential apartments remaining un-booked at completion or first occupation under reverse charge, calculated by prescribed formulas and subject to capped liability. Values of transfers and un-booked apartments are to be deemed equal to similar apartments charged by the promoter nearest the relevant date. Definitions and cross-references to RERA terms are inserted.