When a later price change means another stamp duty return
Later changes to the price
If part of a property price was uncertain, later events can change the SDLT due on the original purchase.
- More tax may require another return and payment.
- Less tax may allow an amendment or repayment claim.
- The current law has separate 14-day and 30-day deadlines.
Scroll down for the full analysis.
Read the original guidance here:
When a later price change means another stamp duty return
If part of your property price depended on something happening later, your stamp duty may need to change too. You may then need to file again. Send HMRC another SDLT return and pay more tax. Sometimes, the result is a repayment instead.
What this rule is about
Some sales include uncertain payments. The parties cannot fix their amount on completion day. It may depend on planning permission, future income or another uncertain event. The law calls this a contingent or uncertain amount, but it simply means the parties have not settled part of the price yet.
You still work out SDLT at the start. For a possible payment, the law assumes payment will happen. For an unknown amount, it uses a reasonable estimate.
What the official source says
HMRC’s manual says that, when the uncertainty ends or the amount becomes known, you should adjust the SDLT position; if extra tax is due, you must send a further return within 30 days and pay it then. That is HMRC guidance.
That is not the whole current statutory position. Finance Act 2003 section 80 sets two different deadlines:
- If the new information makes the purchase notifiable, send a return within 14 days.
- If extra tax becomes due, send a further return within 30 days.
- Use the SDLT rates that applied on the transaction’s effective date.
- Include a fresh tax calculation in the return.
- Pay any extra tax by that return’s filing date.
The manual is HMRC guidance, not law. Its single 30-day statement does not reflect the separate 14-day rule in the current legislation.
What this means in practice
A later payment is not a new property purchase. It changes the tax result for the original purchase. Although the final amount becomes clear later, you must calculate the changed tax using the rate bands that applied on the original transaction’s effective date, rather than later bands. The original rates govern.
- Keep the contract clause that explains the possible payment.
- Record when the deciding event happened.
- Check whether the new facts make the purchase notifiable.
- Recalculate the tax using the original effective-date rates.
- Check whether a payment had previously been deferred.
If the new information means less tax was due, you can amend the original return under section 80 during its amendment period. After that, you can claim a repayment if you did not amend the return.
How to analyse it
Start with the agreement, not the later invoice. Ask why the amount changed. Then ask whether it was uncertain when the property was bought.
- Identify every part of the amount you agreed to pay.
- Ask whether a future event controlled payment or its size.
- Find the date when that event happened, or became impossible.
- Compare the final amount with the estimate used in the first return.
- Work out whether tax has increased, decreased or stayed the same.
- Apply the SDLT rates from the original transaction date.
Example
Amir buys land for £300,000, plus £40,000 if planning permission is granted. His first SDLT calculation assumes the extra £40,000 will be paid. Planning permission is later refused, and it becomes clear that payment will never be due. The SDLT due on Amir’s original purchase may therefore be lower, so he may be able to amend the return or claim repayment.
Why this can be difficult in practice
The contract often creates the difficulty. You must decide what it really says. Parties may describe a sum as a later adjustment, yet it may be a fixed debt, an estimate, or a payment that depends on an uncertain event. Labels do not settle it.
- A payment date is not, by itself, proof that the amount was uncertain.
- More tax can arise even where no money changes hands immediately.
- A linked purchase may also need to be reconsidered.
- Rent has separate rules and is excluded from this adjustment rule.
- Extra tax can attract interest from the original effective date if payment was not deferred.
Key takeaways
- Later facts can change stamp duty on the original purchase.
- The current law may require a return within 14 or 30 days.
- Use the SDLT rates from the original transaction date.
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 — valuing contingent or uncertain amounts paid for land
- FA 2003 section 80 — adjusting tax when an uncertain amount becomes known
- FA 2003 section 87 — interest on unpaid tax after a later adjustment
- FA 2003 section 89 — interest on repayments of overpaid stamp duty
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.
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 contract and any document setting the later payment
- The original SDLT return and tax calculation
- Evidence of the event that fixed the amount or ended the contingency
- The dates of payment, the later event and any deferred-payment arrangement
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 a later price change means another stamp duty 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 - valuing contingent or uncertain amounts paid for land https://www.legislation.gov.uk/ukpga/2003/14/section/51/2025-11-17 - FA 2003 section 80 - adjusting tax when an uncertain amount becomes known https://www.legislation.gov.uk/ukpga/2003/14/section/80/2025-11-17 - FA 2003 section 87 - interest on unpaid tax after a later adjustment https://www.legislation.gov.uk/ukpga/2003/14/section/87/2025-11-17 - FA 2003 section 89 - interest on repayments of overpaid stamp duty https://www.legislation.gov.uk/ukpga/2003/14/section/89/2025-11-17 Guidance page from HMRC on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm05050 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. 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 31 August 2026
Useful article? You may find it helpful to read the original guidance here: When a later price change means another stamp duty return
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