The March 2008 budget heralded major changes to how stamp duty affects purchases of shared ownership properties. Prior to the recent changes, stamp duty was payable on either the full market value of the property at the applicable rate or on the rent and premium. As a result, duty was payable even if you were just buying a small percentage such as 20-40%.
Under the revised rules, duty can be avoided if the price to be paid for the percentage being acquired is less than the stamp duty freshhold of £125,000.00. Duty will remain payable if the price be paid for the share exceeds £125,000.00 or the percentage being purchased exceeds 80%.