New Build Stamp Duty Calculator
Calculate stamp duty on new build properties. Understand SDLT treatment for off-plan purchases, part-exchange deals, and how builder incentives affect your tax liability.
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Enter the full purchase price of the property
Interesting Facts
- SDLT is based on the final purchase price, not build cost.
- Builder incentives can affect the price used for SDLT.
Disclaimer: This tool does not constitute financial advice. We do not recommend taking actions based solely on these results. The calculator makes assumptions and results may be inaccurate due to changes in government policy, interest rates, or personal circumstances. You use this information at your own risk. We can't guarantee to be perfect, so do note you use the information at your own risk and we can't accept liability if things go wrong. For official guidance, visit Gov UK.
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Understanding New Build Stamp Duty
How New Builds are Taxed
New build properties are subject to the same stamp duty rates as existing homes. There is no special relief or surcharge specifically for new builds in England.
Off-Plan Considerations
When you buy off-plan, SDLT is due at completion (when you receive the keys), not at exchange. The completion date determines which tax rates apply.
Part-Exchange Schemes
In a part-exchange, you only pay SDLT on the cash price you pay for the new build, not on the value of your old property that the developer takes in exchange.
New Build Stamp Duty Examples
| Property Price | SDLT (Standard) | SDLT (FTB) | SDLT (Additional) | Effective Rate |
|---|---|---|---|---|
| £250,000 | £2,500 | £0 | £15,000 | 1.0% |
| £400,000 | £10,000 | £0 | £30,000 | 2.5% |
| £500,000 | £15,000 | £6,250 | £40,000 | 3.0% |
| £750,000 | £27,500 | N/A | £65,000 | 3.7% |
FTB = First-Time Buyer (up to £625k). Additional = Additional dwelling surcharge (5%).
Special Considerations for New Builds
Completion Date is Tax Point
SDLT is calculated based on rates in force at the completion date, not when you exchanged contracts. If rates change between exchange and completion, the new rates apply.
- •Plan for potential rate changes
- •Budget conservatively if long build time
- •Monitor HMRC announcements
Builder Incentives Reduce Price
If the developer pays for carpets, white goods, or contributes to your deposit, these generally reduce the purchase price for SDLT purposes, lowering your tax.
- •Incentives reduce taxable amount
- •Get developer confirmation in writing
- •Include in SDLT return accurately
Ground Rent Implications
For leasehold new builds with ground rent, if the NPV of ground rent exceeds thresholds, it can affect SDLT. Most modern leases have low ground rents, minimizing impact.
- •Check NPV calculation in lease
- •Low ground rents usually have minimal effect
- •Solicitor will calculate if applicable
Warranties Don't Affect SDLT
New build warranties (NHBC, Premier Guarantee, etc.) are separate from the property purchase and do not form part of the consideration for SDLT purposes.
- •Warranty costs not included in SDLT
- •Service charges are separate ongoing costs
- •Only purchase price triggers SDLT
Important: Developer SDLT Contributions
If the developer contributes to your stamp duty bill as an incentive, HMRC may treat this contribution as reducing the purchase price for SDLT purposes. This means the developer effectively pays their contribution twice.
Example: On a £300,000 property, if the developer pays your £5,000 SDLT, HMRC may treat the purchase price as £295,000, requiring SDLT of £4,750. The developer still pays £5,000, but you owe less tax. Always clarify how incentives are structured.
Emma Richardson, MRICS
Chartered Surveyor & Property Tax Specialist
Emma Richardson is a RICS-qualified Chartered Surveyor with over 12 years of experience in UK property taxation. She founded Stamp Duty Calculator to help buyers understand the complex world of property transaction taxes.