UK Stamp Duty (SDLT) Calculator

Work out Stamp Duty Land Tax for one purchase of land or property in England or Northern Ireland. Give a price, an effective date and the buyer's circumstances; get the total tax, the effective rate and the tax in each band, with the rates period used and GOV.UK sources. One JSON result goes to the dataset and to the key-value store's OUTPUT record.

Not tax advice. This Actor estimates SDLT from published rate tables. Check the figure with HMRC's own calculator, or a conveyancer, before you file a return.

What it covers

• Residential rates by effective date: the rates from 1 April 2025 1, and the earlier periods from 23 September 2022 2, 3.
• First-time buyer relief: 0% up to the nil-rate threshold and 5% up to the maximum price, with no relief above the maximum 1, 2.
• Higher rates for additional dwellings: 3 percentage points before 31 October 2024 and 5 points from that date, on purchases of £40,000 or more 3, 4.
• Non-UK resident surcharge: 2 percentage points on top of all other residential rates, on purchases of £40,000 or more 5.
• Non-residential and mixed-use rates 6.

Input

{
  "price": 300000,
  "effectiveDate": "2026-06-30",
  "propertyType": "residential",
  "additionalProperty": true
}

• price: required, whole pounds from 1 to 1,000,000,000.
• effectiveDate: required, YYYY-MM-DD, on or after 2022-09-23. Usually the completion date.
• propertyType: residential (default) or nonResidential (non-residential or mixed use).
• firstTimeBuyer, additionalProperty, nonUkResident: optional booleans, residential only. A first-time buyer cannot also be buying an additional property.

Unknown fields are rejected. Do not include names or addresses.

Example output

Selected fields for the input above:

{
  "ratesUsed": "residential",
  "ratesPeriod": {
    "from": "2025-04-01",
    "to": null
  },
  "surchargePercentagePoints": 5,
  "tax": 20000,
  "effectiveRate": 6.67
}

The full result also lists each band (from, to, rate, taxable, tax), notes and source URLs. See examples/output.json.

Limits

One purchase per run, by individuals. Not modelled: leases with rent (net present value), linked transactions, purchases by companies, multiple purchases, and reliefs other than first-time buyer relief. Scotland (LBTT) and Wales (LTT) have their own taxes and are not covered.

If contracts were exchanged before 31 October 2024 but completion was on or after that date, the additional-dwellings surcharge stays at 3% 3. Set pre31Oct2024ContractRelief: true only if that transitional relief has been independently confirmed; otherwise the dated surcharge applies. The Actor does not assess contract variations, assignments or other transitional conditions. Contracts on or before 25 November 2015 are outside scope 3.

Rates must be checked after every Budget. They live in rates.json with the date last checked; an effective date after that date adds a warning to notes. Band calculations retain pennies; the final tax is rounded down to whole pounds 7.

Batch input

Send {"items": [ ... ]} with up to 1,000 inputs, each shaped like the single input above, to get one dataset row per item, each with its index. A bad item gives a row with error instead of failing the run. This suits AI agents (every Apify Actor is also an MCP tool) and bulk users.

Integrations

Ready-made files in integrations/README.md: a Microsoft Power Platform custom connector (Power Automate, Power Apps, Logic Apps, Copilot Studio), OpenAPI 3 (Azure API Management, Postman, n8n, AI agents), an Excel / Power BI Power Query script, a Google Sheets function, and curl, Python and JavaScript examples. Apify's own Zapier, Make and n8n apps and its MCP server work too.

Pricing

Pay per event: one event per successful calculation. Suggested price: $3 per 1,000 calculations.

Local use

With Node.js 22 or later, run node cli.js examples/input.json, or npm test for the worked examples, Actor checks across five time zones and this README check.

Sources

1. GOV.UK: Stamp Duty Land Tax, residential property rates. Accessed 3 October 2026.
2. GOV.UK: Stamp Duty Land Tax rates, 23 September 2022 to 30 October 2024. Accessed 3 October 2026.
3. GOV.UK: Stamp Duty Land Tax rates, 31 October 2024 to 31 March 2025. Accessed 3 October 2026.
4. GOV.UK: Higher rates of Stamp Duty Land Tax (additional residential property). Accessed 3 October 2026.
5. GOV.UK: Rates of Stamp Duty Land Tax for non-UK residents. Accessed 3 October 2026.
6. GOV.UK: Stamp Duty Land Tax, rates for non-residential and mixed land and property. Accessed 3 October 2026.

7. GOV.UK: SDLT calculations and rounding. Accessed 3 October 2026.

AI-generated software draft; manager review required before release.