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Buy-to-Let Stamp Duty Calculator (Additional Property SDLT)

For an additional residential purchase in England and Northern Ireland, higher SDLT rates apply: each standard band plus a 5 percentage point surcharge.

Enter the price in the calculator below (additional-property mode) to see tax due before fees and mortgage maths. Not advice; check HMRC rules for your case.

Last checked:

Calculator

Use 20% or 50000

Loan / LTVn/a
Monthly paymentn/a
Total interestn/a
Total repaidn/a
Interest saved by overpayn/a
Term with overpayn/a
Year-end amortisation
YearInterestCumulative interestBalance
The full picture: costs beyond the mortgage

Optional. Leave closed and the mortgage figures above stay unchanged. England and Northern Ireland SDLT rates as of 1 April 2025 (still current Nov 2026). Scotland (LBTT) and Wales (LTT) differ and are not modelled. Non-UK buyers can pick Custom rate.

Legal, survey, broker. Default 0
What you think the works add to market value
Stamp duty (SDLT)n/a
Total cash needed upfrontn/a
Post-renovation valuen/a
Equity after renovationn/a
Net value createdn/a
LTV before / after renovationn/a

Net value created = value added − renovation − purchase tax − fees (product + other).

SDLT band breakdown (England and NI)
BandRateTaxableTax

Rates source: gov.uk residential SDLT, higher rates page updated 1 April 2025. First-time buyer relief: 0% to £300,000 and 5% from £300,001 to £500,000; no relief if price is over £500,000. Additional property surcharge: 5 percentage points on each band. Not advice.

Real terms: do you actually make money?

Optional. Compares nominal pounds to today's purchasing power. Ignores rent you would otherwise pay, maintenance, insurance and tax on gains. Selling costs are included via the input below (default 0%).

Used to deflate future cash into today's money
Blank = mortgage term
e.g. 2 for agent + legal. Included in the bottom line
Property value at end (nominal)n/a
Property value at end (today's money)n/a
Mortgage payments (nominal total)n/a
Mortgage payments (today's money)n/a
Bottom line gain (nominal)n/a
Bottom line gain (today's money)n/a
Real annualised return on cashn/a

Bottom line = (end property value − remaining loan − selling costs) minus (upfront cash + all mortgage payments made). Upfront cash uses deposit plus any tax/fees/renovation from the full-picture section (0 if left blank). Each future cashflow is deflated by inflation for the real figure. Fixed mortgage payments shrink in real terms when inflation is positive.

Opportunity cost: house vs investing

Optional. Puts the same cash into markets instead of buying. Rent matters: a buyer stops paying rent; an investor still pays it. Enter the rent you would pay instead so monthly investing equals mortgage payment minus rent. Ignores tax wrappers, dividend tax and leverage risk. Past returns are not a forecast.

Reduces the investor's monthly contribution. 0 = ignore rent
Default 10.0%: Damodaran S&P 500 total return CAGR 1928-2025
Default 4.5%: Damodaran US 10-year T.Bond total return CAGR 1928-2025 (long-bond proxy; not a 25-year series)
Default 7.8%: 60% S&P + 40% 10y T.Bond blend of those CAGRs

S&P 500

End portfolion/a
End housing equityn/a
Difference (portfolio − house)n/a
Same in today's moneyn/a

Long US Treasuries (10y proxy)

End portfolion/a
End housing equityn/a
Difference (portfolio − house)n/a
Same in today's moneyn/a

60/40 stocks and bonds

End portfolion/a
End housing equityn/a
Difference (portfolio − house)n/a
Same in today's moneyn/a

Defaults from Aswath Damodaran, Historical Returns on Stocks, Bonds and Bills, NYU Stern, annual total returns 1928-2025 (updated Jan 2026). Geometric (CAGR) means: S&P 500 ≈ 10.0%, US 10-year T.Bond ≈ 4.5%. 60/40 is 0.6×10.0 + 0.4×4.5. Editable. Housing equity = grown house value − selling costs − outstanding loan. Monthly market contributions = mortgage payment − rent.

How much stamp duty on a buy-to-let purchase?

Additional-property SDLT adds 5 percentage points on each England/NI band. A £300,000 additional purchase is £20,000.

What are the additional-property SDLT rates?

From 1 Apr 2025: 5% / 7% / 10% / 15% / 17% on the standard band thresholds (£125k / £250k / £925k / £1.5m).

Is buy-to-let always additional property?

Usually if you already own another dwelling and are not replacing your main home. HMRC replacement rules can change the outcome.

Example: £300k additional-property SDLT

Fixed worked example (not linked to the calculator inputs). England and Northern Ireland higher rates (+5pp on each standard band), from 1 April 2025.

BandPortionRateTax
Up to £125,000£125,0005%£6,250
£125,001–£250,000£125,0007%£8,750
£250,001–£300,000£50,00010%£5,000
Total£300,000£20,000

The formula

Additional-property residential SDLT (England/NI from 1 Apr 2025):
  5% up to £125,000
  7% £125,001 to £250,000
  10% £250,001 to £925,000
  15% £925,001 to £1.5m
  17% above £1.5m
That is standard 0/2/5/10/12 plus 5 percentage points on every band.

Worked example

Additional property, England/NI, purchase price £300,000.

5% × £125,000 = £6,250

7% × £125,000 = £8,750

10% × £50,000 = £5,000

SDLT due = £20,000 (matches the gov.uk worked example cited in DATA_SOURCES.md).

Methodology

How it calculates

  • UK-style amortising (or interest-only) payment from price, deposit, rate and term.
  • Optional full-picture block adds England/NI SDLT bands, fees, renovation and opportunity-cost defaults.

Formula

Additional-property residential SDLT (England/NI from 1 Apr 2025):
  5% up to £125,000
  7% £125,001 to £250,000
  10% £250,001 to £925,000
  15% £925,001 to £1.5m
  17% above £1.5m
That is standard 0/2/5/10/12 plus 5 percentage points on every band.

Assumptions

  • England and NI residential SDLT only in the full-picture block (from 1 Apr 2025). Scotland (LBTT) and Wales (LTT) are not modelled.
  • Opportunity-cost defaults are Damodaran historical CAGRs (editable), not forecasts.
  • No early repayment charges or lender stress tests.

Edge cases

  • First-time buyer SDLT relief applies only if price ≤ £500,000; above that, standard bands apply.
  • Additional-property mode adds 5 percentage points on each standard band.
  • Interest-only payments leave the principal outstanding.
  • Additional-property band table is a fixed worked example at £300,000 (£20,000 tax).
  • Corporate and non-resident surcharges are not modelled.

Sources

Last checked:

FAQ

Is buy-to-let always “additional property”?

Usually for SDLT higher rates if you already own another dwelling and are not replacing your main home. HMRC’s replacement-of-main-residence rules can change the outcome. This tool applies the higher-rate schedule when you select additional property.

Company purchases?

Corporate and non-resident surcharges are not modelled. Use Custom rate on the parent mortgage calculator if you need a flat assumption.

Scotland or Wales?

Not modelled. Those regimes use LBTT and LTT.

Rate date?

Higher rates page updated 1 April 2025; figures verified against gov.uk as of 1 November 2026.

Sources

Rates, rules or specs last checked 1 Nov 2026. Confirm on the official page before you act.

Not financial advice. This calculator is for education only. Double-check results before you make money decisions. Past moves do not predict future ones.