Stamp duty where plans change from six flats to four
In short
HMRC’s example says that cutting an unfinished scheme from six flats to four after full early payment can increase stamp duty. The total price stays the same, but the average price per flat rises.
- Early payment can trigger the original tax calculation.
- A later reduction in planned flats can require a new return.
- The further return is due within 30 days of the change if extra tax is due.
Scroll down for the full analysis.
Read the original guidance here:
Stamp duty where plans change from six flats to four
Full payment before a block is finished can bring stamp duty forward.
If, after full payment but before completion, you cut the number of planned flats and that later change would have produced more tax had it been in place when the tax date first arose, HMRC’s example says more tax may be due, requiring another return within 30 days. The total price may be unchanged.
What this rule is about
Historic relief covered buying several homes. It used an average price per home to work out the tax, rather than taxing the full price as one purchase.
That average matters. When fewer homes are included, the average price rises, even where the total price does not change.
Tax can arise before legal transfer. Early payment can substantially perform a contract. That can mean paying all or almost all of the price early.
What the official source says
HMRC gives an example of a buyer who agrees to buy the freehold of an unfinished block containing six flats for £1.2 million. Before completion, the buyer pays the full price.
Under the contract, the six unbuilt flats count as homes for this purpose. When the buyer pays, the contract becomes substantially performed, and the original stamp duty calculation is made at that point.
- The original calculation uses £1.2 million divided by six: £200,000 per flat.
- Six months later, the parties change the contract to provide four larger flats.
- The total price remains £1.2 million.
- The revised calculation uses £1.2 million divided by four: £300,000 per flat.
- HMRC says it treats the later change as if it happened immediately before early payment.
- As the revised calculation produces more tax, the buyer must make a further return.
HMRC also says the higher rates apply in its example. It also notes that non-UK residence rates may apply if any buyer is not UK resident.
Available facts in the manual do not provide enough detail to check either point independently.
What this means in practice
Layout changes can trigger tax. You cannot assume that keeping the same total price keeps stamp duty unchanged.
What actually decides it? Ask whether the later change would have produced more tax if it had been in place when the tax date first arose.
- Keep the original plans, contract and price breakdown.
- Record the exact date that early payment was made.
- Keep the signed agreement that changes the plans.
- Compare the original number of planned homes with the revised number.
- Rework the tax using the rates that applied on the original tax date.
- Where more tax results, file the further return within 30 days of the change.
The buyer must also pay the extra tax by the filing date for that further return. Missing the change because completion has not happened yet would be an easy mistake.
How to analyse it
Work through the facts in date order. The paperwork matters as much as the final building layout.
- Check whether the contract covered two or more planned homes.
- Find the original tax date, including any early payment date.
- Confirm whether the historic relief was claimed on the original return.
- Identify the later event, such as a formal change of plan.
- Work out whether it happened within the relevant adjustment period.
- Redo the calculation as though the change existed before the original tax date.
- Compare the new result with tax already paid.
- Check higher rates and non-UK residence rates separately, if relevant.
Do not use today’s tax bands for an old transaction. Legislation requires the recalculation by reference to the original tax date.
Example
Here is HMRC’s illustration in plain numbers.
Priya agrees to pay £1.2 million for an unfinished six-flat block and pays the full amount before completion, so the first average is £200,000 per flat. That starts the calculation.
Six months later, the parties change the contract to four flats, still for £1.2 million. The new average is £300,000 per flat. HMRC says the second figure must be used for the historic relief calculation.
If that second figure increases the tax, Priya must report and pay the difference within 30 days of the variation, following the revised historic relief calculation. The deadline is strict.
Why this can be difficult in practice
The effect of later building changes depends on the contract, payment and change details. They do not always have the same effect.
You might think an increase in flats creates the same problem. HMRC ignores increases for this adjustment.
- A draft redesign may differ from a contractual change.
- Payment may or may not amount to substantially all of the price.
- Plans must show what the contract originally required.
- The calculation needs the rate table from the original tax date.
- A buyer’s ownership and residence facts can affect higher rates.
Key takeaways
- Early full payment can set the stamp duty date before completion.
- Reducing planned flats can increase tax despite an unchanged price.
- HMRC says an increase in planned flats is ignored for this adjustment.
Technical analysis
For advisers, and for anyone who wants to check the law behind this page. You do not need this section to understand the guidance above.
Legislation
- FA 2003 section 44 — early performance can set the tax date; when a contract is substantially performed; payment that counts as a substantial amount
- FA 2003 section 55 — how standard stamp duty tax is calculated
- FA 2003 section 58D — statutory basis for multiple homes relief
- FA 2003 Schedule 6B para 2 — purchases involving at least two homes
- FA 2003 Schedule 6B para 3 — meaning of a qualifying multiple-home purchase; meaning of a multiple-home purchase
- FA 2003 Schedule 6B para 5 — averaging method for tax on several homes
- FA 2003 Schedule 6B para 6 — events that can increase tax after relief; treating a later event as earlier; further return and payment after an event; time period for a later adjustment; timing rule after early contract performance
- FA 2003 Schedule 6B para 7 — unbuilt homes included after early payment
Official guidance
The pages below are HMRC’s guidance. Guidance is not law. It sets out how HMRC reads the legislation, and it is not binding on you, on a tribunal or on a court. Where guidance and the legislation differ, the legislation wins. HMRC can also change or withdraw guidance, and it may not cover your facts.
Where this is not settled
- The source does not give the transaction date. That date is needed to confirm the applicable version of the relief, rates and any transitional rules.
- The source does not identify the buyer or give enough facts to independently test the higher rates or non-UK residence rates.
- The actual tax due cannot be calculated from the example alone because the applicable rate table depends on the transaction date.
Evidence you would need
This kind of case is decided on the facts of the individual property. These are the records that usually settle it, and the ones an adviser would ask you for.
- the signed contract and any documents showing what was to be built
- proof of when the full amount was paid
- the formal variation agreement and its date
- plans showing the original and revised number of flats
- the original stamp duty return and payment record
- facts needed to test higher rates and non-UK residence rates
Explore this with an AI
Readers often want to test their own situation. Copy the prompt below into ChatGPT, Claude or Gemini. It hands the model the actual legislation for this page rather than letting it answer from memory, and tells it to be explicit about what is uncertain. What comes back is information, not advice – check it against the links above.
I am researching UK Stamp Duty Land Tax (SDLT), which applies in England and Northern Ireland. MY QUESTION Stamp duty where plans change from six flats to four [Replace this with your own situation: what you are buying, the price, the dates, who the buyer is, and what you plan to do with the property.] THE LAW THIS TURNS ON - FA 2003 section 44 - early performance can set the tax date https://www.legislation.gov.uk/ukpga/2003/14/section/44/2025-11-17 - FA 2003 section 44 - when a contract is substantially performed https://www.legislation.gov.uk/ukpga/2003/14/section/44/2025-11-17 - FA 2003 section 44 - payment that counts as a substantial amount https://www.legislation.gov.uk/ukpga/2003/14/section/44/2025-11-17 - FA 2003 section 55 - how standard stamp duty tax is calculated https://www.legislation.gov.uk/ukpga/2003/14/section/55/2025-11-17 - FA 2003 section 58D - statutory basis for multiple homes relief https://www.legislation.gov.uk/ukpga/2003/14/section/58D/2025-11-17 - FA 2003 Schedule 6B para 2 - purchases involving at least two homes https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/2/2025-11-17 - FA 2003 Schedule 6B para 3 - meaning of a qualifying multiple-home purchase https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/3/2025-11-17 - FA 2003 Schedule 6B para 3 - meaning of a multiple-home purchase https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/3/2025-11-17 - FA 2003 Schedule 6B para 5 - averaging method for tax on several homes https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/5/2025-11-17 - FA 2003 Schedule 6B para 6 - events that can increase tax after relief https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/6/2025-11-17 - FA 2003 Schedule 6B para 6 - treating a later event as earlier https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/6/2025-11-17 - FA 2003 Schedule 6B para 6 - further return and payment after an event https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/6/2025-11-17 - FA 2003 Schedule 6B para 6 - time period for a later adjustment https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/6/2025-11-17 - FA 2003 Schedule 6B para 6 - timing rule after early contract performance https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/6/2025-11-17 - FA 2003 Schedule 6B para 7 - unbuilt homes included after early payment https://www.legislation.gov.uk/ukpga/2003/14/schedule/6B/paragraph/7/2025-11-17 Guidance page from HMRC on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm29981 HOW I WANT YOU TO ANSWER 1. Work from the legislation above. Read it before answering. Guidance from HMRC is its view of the law, not the law, and does not bind a tribunal or a court. 2. Tell me what the rule actually requires, in plain English. 3. Tell me which facts decide the answer, and which facts would change it. 4. Tell me what evidence I would need to support the position. 5. Be explicit about anything unsettled or fact-sensitive. Do not guess. 6. Your training data has a cutoff and SDLT rates and reliefs change at fiscal events. Say so if you are not sure the law is current. POINTS ALREADY KNOWN TO BE UNCERTAIN ON THIS TOPIC - The source does not give the transaction date. That date is needed to confirm the applicable version of the relief, rates and any transitional rules. - The source does not identify the buyer or give enough facts to independently test the higher rates or non-UK residence rates. - The actual tax due cannot be calculated from the example alone because the applicable rate table depends on the transaction date. Do not give me a conclusion you cannot support from the provisions above.
Legislation links show Finance Act 2003 as it stood on 2025-11-17. The law may have changed since, and the rules that apply are those in force on the date of your transaction. The official guidance this page is based on is here.
This page was last updated on 1 September 2026
Useful article? You may find it helpful to read the original guidance here: Stamp duty where plans change from six flats to four
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