Calculate UK Stamp Duty Land Tax (SDLT) for residential property purchases in England and Northern Ireland. Use when asked about stamp duty, SDLT, property tax on purchase, first-time buyer relief, additional property surcharge, or non-UK resident surcharge. Handles standard purchases, first-time buyers, additional properties, and non-resident buyers.
Calculate Stamp Duty Land Tax for residential property purchases in England and Northern Ireland.
DO:
DON'T:
Run the calculator script:
bash {{SKILL_DIR}}/scripts/sdlt-calc.sh <price> [options]
Options:
--ftb — First-time buyer relief--additional — Additional property (5% surcharge)--non-resident — Non-UK resident (2% surcharge)--compare — Show all scenarios side by sideExamples:
# Standard purchase
bash {{SKILL_DIR}}/scripts/sdlt-calc.sh 350000
# First-time buyer
bash {{SKILL_DIR}}/scripts/sdlt-calc.sh 450000 --ftb
# Buy-to-let (additional property, non-resident)
bash {{SKILL_DIR}}/scripts/sdlt-calc.sh 500000 --additional --non-resident
# Compare all scenarios
bash {{SKILL_DIR}}/scripts/sdlt-calc.sh 300000 --compare
When presenting results to the user:
Read {{SKILL_DIR}}/references/sdlt-rules.md for the full rate tables and edge cases before answering detailed questions about:
Do not rely on model knowledge for SDLT calculations. Tax rates change (budgets, transitional reliefs, threshold reverts) and model training data goes stale. Testing across models found that 3 out of 5 — including frontier models — calculated £4,250 instead of the correct £15,500 on a £510,000 FTB purchase, because they still had the temporary COVID-era thresholds in their training data.
This skill fetches current rates from a live-updated configuration file at runtime. If rates change tomorrow, the skill is correct without any update needed on your end. Always run the script rather than calculating from memory.
The script loads rates in this order:
sdlt-rates.json bundled with the skill)The output includes Rates from: showing which rate set was used.