How Stamp Duty Land Tax works
Stamp Duty Land Tax (SDLT) is charged in slices, like income tax — each slice of the price is taxed at its own rate, not the whole price at the top rate. For a standard home mover buying in England or Northern Ireland, the slices from 1 April 2025 are: 0% up to £125,000, 2% on the slice from £125,001 to £250,000, 5% from £250,001 to £925,000, 10% from £925,001 to £1,500,000, and 12% above that. So a £600,000 purchase costs £20,000 in SDLT: nothing on the first £125,000, £2,500 on the next slice, and £17,500 on the rest.
First-time buyer relief
First-time buyers pay nothing on the first £300,000 and 5% on the slice from £300,001 to £500,000 — so a £450,000 first home costs £7,500, and a £300,000 first home costs nothing. The relief has a hard ceiling: above a £500,000 purchase price there is no relief at all, and standard rates apply to the full price. All buyers must be first-time buyers for the relief to apply.
Additional properties
Buying an additional residential property — a second home or a buy-to-let — adds 5 percentage points to every standard band: 5%, 7%, 10%, 15% and 17%. That is why a £300,000 additional property costs £20,000 in SDLT while the same price as a main home costs £2,500. As with every My Knowledge Dock calculator, all maths runs locally in your browser — the figures you type never leave your device. Results are estimates, not financial advice; confirm the final bill with your conveyancer.