Since 1 April 2016 there has been a 3% supplementary Stamp Duty Land Tax (SDLT) charge payable on the purchase of second and subsequent residential properties costing more than £40,000. This was clearly aimed at buy-to-let investors as well as those buying second homes. Note that this additional 3% charge does not apply where the main residence is replaced.
Where the new main residence is bought before the old home is sold the 3% still has to be paid but is refunded if the old home is sold within 36 months.