CHANGE IN STAMP DUTY for properties over £1million. As of the 6th April 2011 a new 5% Stamp Duty Land Tax (SDLT) threshold comes into fruition. If you are selling a house worth over £1 million your buyer will need to pay an extra 1% Stamp Duty on the whole amount. So for a £2 million home it will cost an extra £20,000 to buy.