The concessional rate of GST of 12 percent (effective rate of 8 percent after deducting one-third of the amount charged for the house towards the cost of land) will henceforth (from January 25) be applicable for houses constructed or acquired under the CLSS for Economically Weaker Sections (EWS) / Lower Income Group (LIG) / Middle Income Group-1 (MlG-1) / Middle Income Group-2 (MlG-2) under the Housing for All (Urban) Mission/Pradhan Mantri Awas Yojana (PMAY Urban).
so correct rate is 12% one need to reduce taxable value by 1/3.
for eg 120 rs taxable value tax @ 8% , tax = 9.6
if we go as per law 120 Rs less 1/3rd value of land = Rs 80, tax @ 12% on 80 = 9.60
hope it is clear..