Stamp duty on new build. Favourite Spanish Property Insight › Forums › Spanish Property Forums › Real Estate Topics, News & Discussion › Stamp duty on new build. This topic contains 0 replies, has 1 voice, and was last updated by marios 12 years, 7 months ago. Author Posts September 18, 2006 at 3:21 pm #52247 mariosParticipant How do you work out what stamp duty to pay on a new build when you have bought the plot and built seperately. Author Posts The forum ‘Real Estate Topics, News & Discussion’ is closed to new topics and replies.