Let's cut straight to the chase. The stamp duty land tax (SDLT) you pay on a £400,000 house in the UK isn't a single figure. It depends entirely on your situation. Are you a first-time buyer stepping onto the ladder? A home mover trading up? Or a landlord adding to a portfolio? The bill can range from £0 to over £22,000. That's a massive difference, and getting it wrong can throw your entire moving budget into disarray. I've seen it happen. This guide walks you through the exact calculations, the hidden reliefs you might miss, and how to use the official tools to get your precise number.

In This Article

How UK Stamp Duty Works: The Rules You Need to Know

Stamp Duty Land Tax (SDLT) is a tiered tax. You don't pay one rate on the whole purchase price. Instead, you pay different rates on the portions of the price that fall within specific bands. Think of it like income tax brackets, but for property.

The current rates for residential properties in England and Northern Ireland (Scotland and Wales have their own systems: Land and Buildings Transaction Tax and Land Transaction Tax respectively) are as follows:

Property Price Band Standard Rate (Main Residence) Rate for Additional Properties*
Up to £250,000 0% 3%
£250,001 to £925,000 5% 8%
£925,001 to £1.5 million 10% 13%
Over £1.5 million 12% 15%

*Applies to buy-to-let properties and second homes.

Then there's the First-Time Buyer Relief. This is a game-changer. If you're buying your first ever home, you pay 0% on the first £425,000 (increased from £300,000) and 5% on the portion from £425,001 to £625,000. The property must be your intended main residence, and the purchase price must be £625,000 or less to qualify for any relief.

One nuance most people overlook: these thresholds and reliefs are for England and Northern Ireland. Always double-check if you're buying in Scotland or Wales.

The Exact Calculation for a £400,000 House: Three Real Scenarios

Here’s where we get specific. Let's apply the rules to a £400,000 purchase. I'll walk you through three common buyer profiles.

Scenario 1: The First-Time Buyer

This is the best-case scenario. With the relief, you pay 0% on the first £425,000. Your £400,000 purchase price falls completely within this band.

Calculation: £400,000 x 0% = £0.

That's right. A first-time buyer purchasing a £400,000 home as their main residence currently pays zero stamp duty. This relief alone can save you thousands, money that can go towards furniture, repairs, or your emergency fund.

Scenario 2: The Home Mover (Replacing Your Main Residence)

You own a home and are selling it to buy this new one as your main home. You don't get the first-time buyer relief, but you pay the standard rates.

Calculation:

  • 0% on the first £250,000 = £0
  • 5% on the remaining £150,000 (£400,000 - £250,000) = £7,500
Total Stamp Duty = £7,500.

So, a home mover would pay £7,500. This is the figure most generic online calculators will spit out if you don't tick the "first-time buyer" box.

Scenario 3: The Landlord or Second-Home Buyer

You're buying this property as an additional residence (buy-to-let or a holiday home). The 3% surcharge on top of the standard rates applies.

Calculation:

  • 3% on the first £250,000 = £7,500
  • 8% on the remaining £150,000 (£400,000 - £250,000) = £12,000
Total Stamp Duty = £22,500.

The difference is staggering. The additional property surcharge turns a £7,500 bill into a £22,500 one. This is a critical cost that any prospective landlord must factor into their investment calculations from day one.

The Bottom Line: For a £400,000 house, your stamp duty could be £0, £7,500, or £22,500. Which one applies to you hinges entirely on whether you're a first-time buyer, a mover, or an investor.

How Much Can First-Time Buyers Really Save?

The relief is substantial, but it has precise boundaries. The key condition is that all purchasers must be first-time buyers. If you're buying with a partner or friend and one of you has owned property before, you lose the relief entirely and pay the home mover rates.

The relief phases out at £625,000. If you buy a property for £625,000 or less, you get the relief on the applicable portions. Above £625,000, no relief applies at all. Let's look at a £500,000 purchase for a first-time buyer:

  • 0% on the first £425,000 = £0
  • 5% on the next £75,000 (£500,000 - £425,000) = £3,750
  • Total = £3,750

Without the relief, they'd pay £12,500. That's a saving of £8,750.

Is Stamp Duty Higher for Buy-to-Let or Second Homes?

Yes, significantly. The 3% surcharge was introduced to cool the buy-to-let market and it adds a heavy upfront cost. For a £400,000 property, as we saw, it adds £15,000 to the tax bill (£22,500 vs £7,500).

Many amateur investors underestimate this. They look at the potential rental yield but forget to factor in this substantial capital outlay, which affects their initial return on investment. It's not just a slightly higher percentage; it's a multiplier effect on the lower bands.

How to Use the Government's Stamp Duty Calculator (The Right Way)

The only calculator you should fully trust is the official one from GOV.UK. It's updated with the latest rates and reliefs. Here’s my process for using it accurately:

  1. Have your exact purchase price ready. Not an estimate, the final agreed price.
  2. Know your effective date. This is usually the completion date. Rates can change, so you pay the rates in force on this date.
  3. Answer the buyer status questions honestly. "Are you a first-time buyer?" "Will this be your only or main residence?" "Are you buying an additional property?" Misrepresenting this can lead to penalties.
  4. Review the breakdown. Don't just look at the final figure. The calculator should show you the calculation per band, which helps you understand and verify the math.

I always tell clients to run the calculation twice and save or print the result. It becomes a key part of your budgeting documents.

Common Mistakes & Expert Tips to Save Money

After years of advising on property purchases, the same errors pop up.

Mistake 1: Ignoring the 'Effective Date'. Your liability is fixed on the date you "substantially perform" the contract, typically completion. If you exchange contracts in June but complete in September, and rates change in August, you pay the September rates. This timing matters.

Mistake 2: Forgetting About the Surcharge in Complex Purchases. If you're moving but struggling to sell your old home, and you complete on the new one before selling the old one, you'll temporarily own two properties. You will likely have to pay the higher surcharge rates upfront. You can claim a refund if you sell your previous main residence within 36 months, but it ties up cash flow.

Tip 1: Budget for More Than Just Stamp Duty. Your moving budget needs to cover legal fees, survey costs, removals, and potentially mortgage product fees. Stamp duty is the biggest chunk, but it's not the only one.

Tip 2: Understand Joint Purchases. If one buyer is a first-timer and the other isn't, you don't qualify for the relief. Some couples in this situation consider having only the first-time buyer on the mortgage/title to secure the saving, but this has major implications for mortgage affordability and legal ownership. Get professional legal advice.

Tip 3: Explore Potential Reliefs for Uninhabitable Properties. This is a lesser-known area. If you're buying a derelict property that is not suitable for immediate habitation, there's an argument it may not be subject to residential SDLT rates but potentially lower non-residential rates. The definition is strict, but for major renovation projects, it's worth a discussion with your solicitor.

Your Stamp Duty Questions, Answered

My partner owns a flat abroad. We're buying a £400k house together as our main UK home. Are we first-time buyers?
No. First-time buyer relief requires that neither purchaser has ever owned an interest in a residential property anywhere in the world. Ownership abroad disqualifies you. You would pay the standard home mover rate of £7,500, or the additional property rate if the overseas property is still owned and considered a dwelling.
Does the date I exchange contracts or complete change my stamp duty bill?
The "effective date," usually your completion date, is what locks in the SDLT rates you pay. The date you exchange contracts doesn't typically matter for SDLT purposes, unless a special clause is involved. Always budget based on the rules expected to be in force on your planned completion date.
What exactly counts as an 'additional property' for the 3% surcharge?
It's any residential property that is not replacing your main residence. This includes buy-to-let properties, holiday homes, and even a property you buy for a family member to live in if you retain ownership. If you own any other residential property (anywhere in the world) at the end of the day of completion, the surcharge likely applies. There are limited exemptions, like for caravans and houseboats.
I'm an overseas buyer. Do I pay more stamp duty on a £400k UK home?
Possibly. Since April 2021, non-UK residents may pay a 2% surcharge on top of all other applicable rates (standard or additional property rates). You need to check your residency status for SDLT purposes, which has a specific test. This is a complex area where specialist tax advice is crucial.
Can I add my stamp duty bill to my mortgage?
Technically, some lenders might allow you to increase your mortgage to cover costs, but it's generally a bad idea. You'd be borrowing money for a tax bill at your mortgage interest rate, repaying it over 25-30 years, which dramatically increases the total cost. It's far better to save for it as part of your deposit and moving costs.