The Department's attempt to trigger Rule 42 reversal by treating the statutory 1/3rd land abatement as an "exempt supply" is a jurisdictional error that confuses a valuation measure with a taxable event. Under the Govind Saran mandate (1985 (4) TMI 65) , the 1/3rd deduction is a legal fiction used solely to determine the "Measure" of the taxable construction service, not to vivisect an indivisible composite supply into a separate sale of land.
Since the "Consideration" is paid in respect of a taxable residential unit and all inputs are physically consumed to create that unit-not the earth beneath it-there is no "dual use" of inputs. Judicially, following the logic in Munjaal Manishbhai Bhatt (Gujarat HC) ( 2022 (5) TMI 397), the land component is incidental to the taxable supply of construction; thus, a valuation mechanism cannot be used to manufacture an "exempt supply" reality where none exists.
You may effectively defend on this legal position.