I have booked a flat in Gujarat state (under construction) in Oct'2016. Banakhat and allotment letter was given to me that time. The property value is 21,75,000/-. Out of that I have made payment of 20,00,500/-. Now balance 1,70,000/- is pending from my home loan. Builder asked me to pay service tax on the payment made to builder @ 4.5% which is 90,225/- before GST rollout. The construction is completed and we are about to do the final registration of the property in Oct'2017. Now the builder is asking for GST charges @ 12% on the pending payment (1,70,000/-).
Please advice should I pay the GST on balance amount @ 12% or it should be @ 4.5%. Also advice rate of stamp duty for the registration of the property in Gujarat.