If you are paying for your house in installments to the builder you may end up paying 12% GST on payments due from July 1 onwards, instead of 4.5% service tax that you paid on installments till June 30. Builders claim that the 7.5% increase (12% - 4.5%) in tax post GST is because they will not be able to claim any credit for taxes paid on inputs bought before July 1. Many developers have already issued letters to buyers asking them to be ready to pay higher taxes on the remaining amount.