When the surcharge applies
If, at the end of the day you complete, you own two or more residential properties anywhere in the world and you are not replacing your main residence, the purchase is an "additional property" and 5 percentage points are added to every SDLT band. A property worth under £40,000 is ignored, as is a share in an inherited property of 50% or less within three years of inheriting.
The calculation
Standard bands from 1 April 2025: 0% to £125,000, 2% to £250,000, 5% to £925,000, 10% to £1.5 million, 12% above. For an additional property these become 5/7/10/15/17%. On a £450,000 buy-to-let: £12,500 standard plus 5% × £450,000 = £22,500 surcharge, total £35,000 — 7.8% of the price.
Replacing your main home
Buying a new main residence while still owning the old one triggers the surcharge, but you can reclaim it if you sell the previous main home within 36 months. Claim online from HMRC within 12 months of the sale. If you sold the old home first, the surcharge does not apply at all.
Couples, companies and overseas property
Married couples and civil partners are treated as one unit: if either owns a property, both are caught. Unmarried partners are assessed individually. Limited companies always pay the surcharge (and 17% flat above £500,000 in some cases). A flat you own in Dubai or an apartment in Lahore counts as a property you own.
Non-UK residents
Buyers who have spent fewer than 183 days in the UK in the 12 months before completion pay a further 2% on every band — on top of the 5% if it is also an additional property. The 2% is refundable if you then spend 183 days in the UK in the following 12 months. Gulf-based British expats buying a UK rental typically pay 7/9/12/17/19%.
Scotland and Wales
Scotland's LBTT adds an 8% Additional Dwelling Supplement on the whole price; Wales's LTT higher rates add 5 points to each band from the first pound. Use the LBTT and LTT calculators for those.