If you used the HMRC stamp duty calculator before buying your home, you almost certainly typed in the full purchase price. The calculator returned a number, your solicitor collected that amount, and you paid it. Job done.
Except the calculator didn't ask you a crucial question — one that could have reduced your bill. It didn't ask whether moveable items (chattels) were included in the purchase price.
The problem
The HMRC stamp duty calculator at GOV.UK asks for one thing: the purchase price. It then calculates SDLT on that full amount. There is no field for chattels. No prompt asking whether moveable items were included. No mention that the law requires a "just and reasonable" apportionment between land and any other subject matter of the transaction.
For most residential purchases, the price agreed between buyer and seller includes everything in the property — the building, the land, and all the contents like carpets, curtains, white goods, and light fittings. When you enter that full figure into the calculator, it treats the entire amount as taxable.
But not all of it should be.
What the law actually says
Finance Act 2003, Schedule 4, Paragraph 4 is clear: the chargeable consideration for SDLT must be apportioned on a "just and reasonable" basis between land and any other subject matter of the transaction.
Chattels — moveable items like carpets, curtains, freestanding appliances, and furniture — are "other subject matter." They are not land. They are not part of the building. And SDLT is a tax on land transactions, not on buying someone's curtains.
The legal position
HMRC's own guidance (SDLTM04020) confirms that chattels should be excluded from the chargeable consideration. This isn't a loophole or aggressive tax planning — it's what the legislation explicitly requires.
So is the calculator "wrong"?
Technically, no. The calculator does exactly what it says it does: it calculates SDLT on the amount you enter. If you enter £500,000, it calculates SDLT on £500,000. It makes no claim about whether that £500,000 is the correct amount to calculate on.
The issue is that most people enter the full purchase price, which includes chattels. The calculator doesn't tell you not to do this. It doesn't prompt you to deduct the value of moveable items. It doesn't mention that the law requires an apportionment.
It's not wrong — it's incomplete. And that incompleteness costs most homebuyers money.
The numbers: how much this costs you
Let's say HMRC's calculator tells you the SDLT on a £500,000 property is £12,500. Your property includes £8,000 of chattels — carpets, curtains, white goods, and some furniture the sellers left behind.
The correct chargeable consideration should be £492,000, not £500,000. The SDLT on £492,000 is £12,100. You've overpaid by £400 because the calculator didn't ask the right question.
At higher property values, the gap widens:
| Price entered | Chattels | HMRC says | Correct SDLT | Overpaid |
|---|---|---|---|---|
| £350,000 | £5,000 | £5,000 | £4,750 | £250 |
| £500,000 | £8,000 | £12,500 | £12,100 | £400 |
| £750,000 | £15,000 | £25,000 | £24,250 | £750 |
| £1,000,000 | £20,000 | £41,250 | £39,250 | £2,000 |
| £1,500,000 | £35,000 | £93,750 | £90,250 | £3,500 |
Based on standard residential SDLT rates from April 2025 with estimated chattel values.
Why doesn't HMRC fix this?
Good question. The most charitable explanation is that HMRC's calculator is designed to be simple. Adding a chattels field would require guidance on what qualifies, how to value items, and how to distinguish fixtures from chattels. That complexity could lead to errors and disputes.
The less charitable explanation is that an incomplete calculator consistently results in higher SDLT payments — which suits HMRC fine. They're not going to volunteer a tool that reduces their tax revenue.
Whatever the reason, the result is the same: millions of homebuyers use a calculator that doesn't account for a legally valid deduction. Most never find out.
What our tools do differently
Our SDLT calculator does the same standard stamp duty calculation as HMRC's — we're not reinventing the rates. Where we differ is that we also provide a refund estimator that helps you identify and value the chattels in your property, then shows you the SDLT difference.
This is the step that HMRC's calculator misses entirely. And it's the step that could save you hundreds or thousands of pounds.
What to do about it
If you've already bought a property and paid SDLT based on the full purchase price without deducting chattels, you can claim a refund from HMRC. You have 4 years from the transaction date to submit an overpayment claim.
If you haven't bought yet, make sure your solicitor apportions chattels correctly on the SDLT return. Don't rely on HMRC's calculator as the final word — it was never designed to give you the complete picture.
Try our calculator — then check your refund
See what HMRC's calculator told you to pay. Then see what you should have paid.