Real estate sector: conditional GST rates and ITC rules tying lower tax treatment to option exercise, invoicing and supplier registration. Prescribes differentiated State tax treatment and conditional lower tax rates for construction services in REPs and RREPs, links eligibility to timing of consideration and a one time option, and conditions input tax credit by an 80% registered supplier threshold with reverse charge on shortfalls and specific rules for cement from unregistered suppliers; Annexures provide formulae for apportioning and transitioning ITC using carpet area, booking, invoicing and completion factors.