When the final property price is known after your SDLT return
When a later payment changes stamp duty
A final property price can change the SDLT due on the original purchase. The key date for the tax calculation is normally the original transaction date.
- Keep evidence of the estimate and final amount
- Check whether the deal has become notifiable
- Do not rely on the manual’s older 30-day statement without checking the current rule
Scroll down for the full analysis.
Read the original guidance here:
When the final property price is known after your SDLT return
When the final property price is known after your SDLT return
If the price you pay for a property was only an estimate at first, stamp duty may need another look when you know the final amount. You may need to send HMRC more information, pay extra SDLT, or claim money back. Timing matters.
What this rule is about
Sometimes a property deal includes a later payment. It may depend on an event that has not happened yet, or nobody may know the amount when you complete.
For the first SDLT return, the law allows a reasonable estimate where the price is uncertain. Once the event happens, or the parties work out the exact amount, section 80 can require you to reconsider the SDLT position.
That can change more than the tax bill. It can also change whether the deal needed an SDLT return at all.
What the official source says
HMRC’s manual describes three broad situations. It says that you should identify the original return, give the final price, work out any SDLT now due, and make any payment required.
- If you filed an SDLT return showing no tax, and the final price is higher, HMRC says to send details of the change and any tax due.
- If you filed a return and paid SDLT on an estimate, HMRC says to report the final price.
- If the estimate was too low, HMRC says extra SDLT should be paid.
- If the estimate was too high, HMRC says you can seek a refund.
- If you did not file because the estimate was below the notification threshold, compare the final price with the threshold in force on the original transaction date.
- If the final price remains below that threshold, HMRC says you need take no action.
- If it is now above the threshold, HMRC says to make an SDLT return using the real price and original effective date.
There is an important update. The manual says a return in that last situation must be made within 30 days. The supplied text of Finance Act 2003 section 80 now says 14 days where new information makes a transaction notifiable.
Where tax was not due before, but becomes due, or where more tax is due, section 80 gives 30 days for a further return. The return must include a tax calculation, and you must pay the tax by that deadline.
What this means in practice
Do not treat a later payment as separate from the purchase. It can change the stamp duty due on the original deal. Calculate the tax using the rules that applied on the original effective date.
This is the point people miss: you may know about a later payment months after completion, but the calculation looks back to the original transaction date.
- Keep the reference number from your first SDLT return.
- Keep the contract, completion papers, and terms for any later payment.
- Record the day the uncertain amount became known.
- Rework the SDLT using the original transaction date.
- Check whether the new information makes the deal notifiable.
- Pay extra SDLT by the deadline if it is due.
- Consider an amendment or repayment claim if you paid too much.
Interest can still be costly. For an under-estimate where you did not defer payment, the law says interest on extra SDLT runs from the original effective date. It does not wait until you know the final price.
For a repayment, the law provides interest from the date HMRC received the overpaid tax. That is different.
How to analyse it
Start with the paperwork, not the final figure alone. You need to know why the price changed and exactly when that change became certain.
- Was part of the price conditional on a future event?
- Or was the amount simply unknown when the property was bought?
- What reasonable estimate did you use in the original SDLT return?
- When did the condition happen, fail, or become clear?
- When was the final amount first known?
- Does the final amount make the transaction notifiable?
- Is extra SDLT due, or has too much been paid?
- Was payment deferred under section 90?
A deferment can change the result. Section 90 allows an application to defer SDLT in limited cases involving a conditional or uncertain later payment. It does not cover rent, and it does not remove SDLT due on amounts already fixed.
Example
Amir buys a property for £240,000, plus a possible £40,000 later payment if a stated event happens. His original SDLT position uses an estimate based on the facts then known. Eight months later, the event happens and the extra £40,000 becomes payable.
Amir must revisit the SDLT calculation using the original effective date, not the date of the later payment. If more SDLT is due, he must make the required further return within 30 days and pay it. Interest may run from the original effective date unless Amir deferred payment.
Why this can be difficult in practice
The hard part often involves deciding when the parties first knew the amount. A payment can be discussed, disputed, or calculated in stages. That is not always the same as the parties finally working it out.
You might think the date money changes hands decides everything. It does not. The key facts can be the contract terms, the event that triggers payment, and when the amount became certain.
- A later payment is not automatically outside the SDLT calculation.
- An estimate must have been reasonable when it was used.
- The original transaction date still controls the SDLT calculation.
- A late return can lead to penalties.
- The source manual’s filing instruction may not reflect the current statutory 14-day rule for a newly notifiable deal.
- HMRC’s stated postal process should be checked before you rely on it.
Key takeaways
- Revisit SDLT when an estimated or conditional price becomes known.
- Use the original transaction date to calculate any change.
- Check promptly whether a 14-day or 30-day return deadline applies.
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 51 — estimates for uncertain or conditional property prices
- FA 2003 section 80 — adjusting SDLT when the final price becomes known
- FA 2003 section 87 — interest on SDLT that remains unpaid
- FA 2003 section 89 — interest on repayments of overpaid SDLT
- FA 2003 section 90 — deferring SDLT on certain later payments
- FA 2003 Schedule 10 para 2 — meaning of the filing date for returns
- FA 2003 Schedule 10 para 3 — penalties for late SDLT returns
- FA 2003 Schedule 10 para 6 — changing a return and supporting a repayment
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 appropriate current HMRC method and address for sending a further return should be checked before filing.
- The source page’s reference to a letter to the Birmingham Stamp Office may describe an administrative practice rather than a legal requirement.
- Current law after 17 November 2025 has not been verified against the official legislation website.
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 original SDLT return reference number
- the contract and papers showing the estimated price
- evidence of when the final amount became known
- a calculation using the original transaction date
- proof of SDLT already paid and any further payment
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 When the final property price is known after your SDLT return [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 51 - estimates for uncertain or conditional property prices https://www.legislation.gov.uk/ukpga/2003/14/section/51/2025-11-17 - FA 2003 section 80 - adjusting SDLT when the final price becomes known https://www.legislation.gov.uk/ukpga/2003/14/section/80/2025-11-17 - FA 2003 section 87 - interest on SDLT that remains unpaid https://www.legislation.gov.uk/ukpga/2003/14/section/87/2025-11-17 - FA 2003 section 89 - interest on repayments of overpaid SDLT https://www.legislation.gov.uk/ukpga/2003/14/section/89/2025-11-17 - FA 2003 section 90 - deferring SDLT on certain later payments https://www.legislation.gov.uk/ukpga/2003/14/section/90/2025-11-17 - FA 2003 Schedule 10 para 2 - meaning of the filing date for returns https://www.legislation.gov.uk/ukpga/2003/14/schedule/10/paragraph/2/2025-11-17 - FA 2003 Schedule 10 para 3 - penalties for late SDLT returns https://www.legislation.gov.uk/ukpga/2003/14/schedule/10/paragraph/3/2025-11-17 - FA 2003 Schedule 10 para 6 - changing a return and supporting a repayment https://www.legislation.gov.uk/ukpga/2003/14/schedule/10/paragraph/6/2025-11-17 HMRC's guidance page on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm50310 HOW I WANT YOU TO ANSWER 1. Work from the legislation above. Read it before answering. HMRC guidance is HMRC's 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 appropriate current HMRC method and address for sending a further return should be checked before filing. - The source page's reference to a letter to the Birmingham Stamp Office may describe an administrative practice rather than a legal requirement. - Current law after 17 November 2025 has not been verified against the official legislation website. 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: When the final property price is known after your SDLT return
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