I think artbrooks is right. You may already have looked at the HM Revenue and Customs website. You do need to look at it carefully because there is a sliding scale for second houses so after so many years you only pay on a certain percentage of the amount you sell it for. This could apply to building plots so it is worth looking into. My sister sold a garage that she bought and paid an accountant to work out the capital gains. He saved her thousands of pounds.