The Stamp Duty for Sale Agreement is 0.1% of the Sale Consideration or Guidance Value whichever is higher in Bangalore. You as the buyer will have to pay it. However, please note that this 0.1% can be adjusted at the time of paying the Stamp Fee for the Sale Deed Registration. You should keep the Sale Agreement and Receipt safely as this needs to be produced at the time of Sale Deed registration for claiming adjustment towards the stamp fee paid.