When a later payment changes your stamp duty bill
Later payments and SDLT
Where part of a property price depends on future events or is not yet known, SDLT starts from an assumption or reasonable estimate. The position may then change when the facts are settled.
- More tax can trigger a new return and payment.
- Less tax can allow an amendment or repayment claim.
- The original transaction date determines the tax rules used.
Scroll down for the full analysis.
Read the original guidance here:
When a later payment changes your stamp duty bill
If part of your property price depends on something that happens later, your stamp duty bill may change too. SDLT starts with an assumed or estimated figure. Once the real figure is known, you may need to pay more, or you may be able to recover an overpayment if your original payment exceeded the amount due. The bill can change.
What this rule is about
Some deals include an extra payment that remains unsettled at completion because it depends on planning permission, future sales, or another event that may never occur. SDLT cannot wait. It does not wait until everything is known.
The law requires a starting figure. Later facts can then change it.
What the official source says
HMRC’s manual says that taxpayers can adjust SDLT once they determine the amount paid for the transaction. The legislation gives the detail.
- If a payment depends on an uncertain future event, SDLT starts by assuming that you will pay it, even though the event may not happen and the amount may never become due. That is the starting point.
- If the amount is uncertain or unknown, SDLT starts from a reasonable estimate.
- When the event happens, or clearly will not happen, HMRC reconsiders the SDLT position.
- The same can happen when a relevant amount or instalment becomes known.
What this means in practice
A later payment can increase the tax due. If new information makes the deal notifiable, a return is due within 14 days. In other cases, where more tax is due after the amount becomes known but the deal does not newly become notifiable, you must file a further return and make payment within 30 days. Act promptly.
- Use the tax rules that applied on the original effective date.
- Keep evidence of the original estimate and the final outcome.
- Check linked property deals too, as they can also need reconsidering.
How to analyse it
Start with the contract, not the label used for the payment. Ask what was known when you completed.
- Is any part of the price conditional on a future event?
- Was the amount unknown, or was only payment delayed?
- What estimate did you use in the original SDLT return?
- When did the event become certain or the amount become known?
- Does the new figure mean more tax or less tax?
Example
Amir buys land for £300,000, plus £20,000 if the planning authority grants planning permission. SDLT initially treats the extra £20,000 as payable. If the planning authority later refuses planning permission and cannot grant it, the SDLT calculation may reduce. If the planning authority grants it, the original assumption remains the relevant starting point.
Why this can be difficult in practice
People often confuse an unknown price with a fixed price that they will pay later, although the distinction matters because the former can require an estimate. They are different. Amount or liability must depend on uncertainty.
- A vague payment clause may need careful reading.
- An estimate must be reasonable when the return is made.
- Rent has separate SDLT rules and is excluded from this route.
- There are limits on some lease-related repayment claims.
Key takeaways
- Unknown future payments do not always postpone SDLT.
- Later facts can mean more tax or a repayment.
- Keep the contract and proof of when the amount became known.
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 payments that depend on future events
- FA 2003 section 80 — adjusting SDLT when later facts become known
- FA 2003 Schedule 10 para 6 — time limit for amending an SDLT return
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
- It can be fact-sensitive whether a payment truly depends on an uncertain future event, or whether its amount was already fixed.
- The date when an amount becomes known can matter for filing and payment duties.
- A lease transaction may face limits on a repayment claim in some circumstances.
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 side agreement
- Details of the future event or payment formula
- Evidence showing when the event was resolved
- The original SDLT return and payment record
- Documents supporting the final amount paid
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 payment changes your stamp duty bill [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 payments that depend on future events https://www.legislation.gov.uk/ukpga/2003/14/section/51/2025-11-17 - FA 2003 section 80 - adjusting SDLT when later facts become known https://www.legislation.gov.uk/ukpga/2003/14/section/80/2025-11-17 - FA 2003 Schedule 10 para 6 - time limit for amending an SDLT return https://www.legislation.gov.uk/ukpga/2003/14/schedule/10/paragraph/6/2025-11-17 Guidance page from HMRC on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm05040 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 - It can be fact-sensitive whether a payment truly depends on an uncertain future event, or whether its amount was already fixed. - The date when an amount becomes known can matter for filing and payment duties. - A lease transaction may face limits on a repayment claim in some circumstances. 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 payment changes your stamp duty bill
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