Hi , I bought a flat with reputed builder, but the property is not registered under reara ,It was in prelaunch and he took the 20% without the contract was ready , then they asked for 85% within 6 months and then for 15% work they took 2 years , the possesion was in August 2017 but even after saying project is goign very fast to collect the 85% money they moved to grace period and by then GST came in picture , they applied for OC on APRIL 2017, as per my understanding the OC is only applied when property is complete an hence GST should not be applicable , but these guys are saying that GST is applicable on full 15% . Is it legal and where I can approach to complain the same? Is going to consumer forum will help? they are asking 230000 extra ,