How the Stamp Duty Calculator Works — Methodology

Methodology: how the calculator works

1. Sources — official only

Every rate and threshold used on this site comes from the official publisher for that tax:

  • England and Northern Ireland (SDLT): GOV.UK Stamp Duty Land Tax guidance
  • Scotland (LBTT): Revenue Scotland
  • Wales (LTT): GOV.WALES and the Welsh Revenue Authority

We do not take rates from other calculators, blogs, or AI-generated summaries. When an official source changes a rate, this site changes with it — never the other way round.

2. The calculation

For the price you enter, the calculator applies the published bands marginally (each slice of the price is taxed at the rate for its band) for your chosen nation and buyer type, then adds any applicable extras:

  • First-time buyer relief (England and Northern Ireland): 0% on the first £300,000, 5% on £300,001–£500,000; no relief above £500,000.
  • Additional-property surcharge (England and Northern Ireland): +5 percentage points on each band since 31 October 2024, applying to purchases of £40,000 or more.
  • Non-UK resident surcharge (England and Northern Ireland): a further +2 percentage points.
  • Scotland: standard LBTT bands, with the nil-rate band raised to £175,000 for first-time buyers (maximum relief £600); an 8% Additional Dwelling Supplement on the full price for additional dwellings (since 5 December 2024).
  • Wales: LTT bands (no first-time buyer relief), plus the higher residential rates for additional dwellings (since 11 December 2024).

The result page shows the total, the effective rate, and a band-by-band breakdown so you can see exactly where each pound of tax comes from.

3. Verification

  • Worked examples. The calculator’s logic was checked against 24 official worked examples from the three tax authorities (for instance GOV.UK’s £295,000 example = £4,750 SDLT, and the Welsh Revenue Authority’s £260,000 higher-rate example = £15,950 LTT) — all matched.
  • Dated stamp. Every page carries a “Rates verified” line with the month and year of the last check. The current stamp is October 2026.
  • Re-checks. Rates are re-verified against the official sources after each UK Budget and Scottish/Welsh fiscal event, and after any announced rate change. Changes at Budgets can take effect immediately, so the check happens the morning after.

4. What the calculator does not cover

To stay accurate, the calculator sticks to standard residential purchases. It does not model:

  • shared ownership and staircasing,
  • mixed-use or commercial property,
  • purchases by companies or other non-natural persons (a flat 17% rate applies above £500,000 in England and Northern Ireland),
  • leasehold-specific rules, reliefs for first-time buyers in Scotland beyond the standard LBTT relief, and other edge cases.

If any of these apply to you, treat the figure as a starting point and confirm it with your conveyancer or solicitor.

5. Corrections

If you spot an error, please report it via the Contact page with the price, nation and buyer type you entered and the official source that disagrees. Confirmed errors are corrected promptly and the page’s “Rates verified” date is updated.