SDLT for Property Developers: Rates, Additional Dwelling Supplement, and How to Minimise

SDLT: The basics for property developers

Stamp Duty Land Tax (SDLT) is a tax on the purchase price of a property in England and Northern Ireland (Scotland has LBTT; Wales has LTT). For property developers, SDLT is almost always levied at the higher rate — because you're buying an additional dwelling (you already own your own home, or the business owns property). The additional dwelling surcharge of 5% applies on top of the standard rates from the first pound.

2025/26 SDLT rates for additional dwellings

The standard residential SDLT rates (as of 2025/26) are:

Property Value	Standard Rate	Additional Dwelling Rate (inc. 5% surcharge)
Up to £250,000	0%	5%
£250,001–£925,000	5%	10%
£925,001–£1,500,000	10%	15%
Over £1,500,000	12%	17%

The rates are applied in bands — like income tax — so on a £350,000 purchase as an additional dwelling:

• First £250,000 at 5% = £12,500
• Next £100,000 at 10% = £10,000
• Total SDLT: £22,500

Compare this to a first-time buyer purchasing the same property at £350,000, who would pay zero SDLT (first-time buyer relief applies up to £500,000 for properties under £625,000). That's a £22,500 cost disadvantage for the developer. This is why getting the SDLT calculation right in your appraisal is so important.

When does the additional dwelling surcharge apply?

The 5% surcharge applies if, at the end of the transaction, the buyer owns two or more dwellings. This catches:

• Individuals who own their own home and are buying an investment or development property
• Companies buying residential property (companies always pay the surcharge)
• Partnerships and trusts in most circumstances

If you are replacing your only main residence, you won't pay the surcharge (subject to conditions). But for virtually all development purchases, you should assume the surcharge applies.

SDLT reliefs available to developers

Multiple Dwellings Relief (MDR)

If you're buying multiple dwellings in a single transaction — for example, a portfolio of flats in one block — you may be able to claim Multiple Dwellings Relief. MDR calculates SDLT based on the average price per dwelling rather than the total transaction price, which can significantly reduce the bill on higher-value transactions. Note: MDR does not remove the 5% additional dwelling surcharge.

Mixed-use / non-residential rates

If you're buying a mixed-use property (e.g., a property with a commercial ground floor and residential flats above), the entire transaction may qualify for non-residential SDLT rates, which are significantly lower (0% up to £150,000, 2% £150,001–£250,000, 5% above). This can produce substantial savings on acquisitions of larger mixed-use buildings.

Linked transactions

If you're buying multiple properties from the same seller, HMRC may treat them as linked transactions and apply the higher rates across the whole. Get specialist tax advice before structuring a deal like this.

Reclaiming the SDLT surcharge

In very limited circumstances, you can reclaim the 5% surcharge paid on a purchase — specifically if you sold your previous main residence within 3 years before the new purchase, and the new property is now your only residential property. This doesn't apply to most developer scenarios, but it's worth knowing.

SDLT on off-plan purchases

If you're buying off-plan (contracts exchanged before construction is complete), SDLT is calculated on the purchase price at exchange, not on the completion price. If there's a significant time between exchange and completion, there's a risk that SDLT rates change — so factor this into your risk assessment.

Practical tips for minimising SDLT

1. Always run the calculation before submitting an offer. SDLT is a significant cost that affects your maximum viable purchase price. A dedicated calculator like Marginly handles this automatically for every deal.
2. Consider mixed-use properties. The non-residential SDLT rates are much lower, making mixed-use acquisitions disproportionately attractive from a tax perspective.
3. Get specialist tax advice on portfolio purchases. MDR and linked transaction rules are complex — the cost of advice is trivial compared to the potential SDLT savings on a multi-property deal.
4. Don't forget SDLT is cash on day one. Unlike build costs that are paid over time, SDLT is due within 14 days of completion. It all comes out of your cash reserves on the day of purchase.