When a later payment means you must update your SDLT
Later payments and SDLT
When a future part of a property price becomes known, the original SDLT calculation may change. You may need to file a return, make a further return, pay extra tax or claim a repayment.
- A first-time reportable purchase has a 14-day return deadline.
- Extra tax usually requires a further return within 30 days.
- Use the tax rules that applied on the original purchase date.
Scroll down for the full analysis.
Read the original guidance here:
When a later payment means you must update your SDLT
If your property price depended on something happening later, that later event can leave stamp duty unfinished on completion day.
When the event happens and fixes the amount, you may need to tell HMRC, pay more tax or ask for money back.
What this rule is about
Some property deals include a later payment. For example, a buyer can agree to pay more if land is sold on, planning is granted or a business reaches a set result.
At the start, the future payment may be uncertain. The buyer must use a value then.
Once the uncertainty ends, the buyer should check the original SDLT position again.
This is not just an update to the paperwork. It can change the tax due on the purchase.
What the official source says
HMRC’s manual says that, when tax payment was deferred and the future amount becomes known, you must notify HMRC within 30 days, quote the deferment reference, and include payment details.
This is HMRC’s guidance.
The legislation has a wider rule. It applies when a condition happens, will not happen, or an uncertain amount becomes fixed. It sets different deadlines depending on what the new information changes.
- If the new information makes the purchase reportable, send a return within 14 days.
- If extra tax is due without making the purchase reportable, send a further return within 30 days.
- The further return must include a calculation of the tax due.
- Pay any tax due by the deadline for that return.
- Work out the tax using the rules that applied on the original effective date.
- HMRC says a later notification for an already reported purchase should be sent as a letter.
- Where several plot sales occur in one month, HMRC says the letter should list each sale and the tax for each one.
HMRC’s manual is guidance, not law. HMRC tells you to use a letter as part of its process, but the law refers to a further return.
What this means in practice
Check SDLT before the deal ends.
The date the payment becomes fixed, or the condition is settled, can start a short deadline.
If you had an accepted arrangement to defer tax, keep its reference number with the contract. You may need it when you notify HMRC.
- Keep the contract clause that explains the later payment.
- Record the exact date when the event happened or failed.
- Keep sale statements, completion papers and payment records.
- Revisit the whole price, not only the extra sum.
- Check whether the original purchase was ever reported to HMRC.
- Pay the extra amount by the filing deadline if more tax is due.
The whole-price point matters. A later payment can move the total into a different tax calculation. You should not simply apply a rate to the extra payment on its own.
How to analyse it
Start with the contract. Ask what was uncertain on the purchase date, what has now changed, and whether that change alters the SDLT calculation under the rules that applied on the original effective date.
Then identify the answer.
- Was part of the property price conditional, uncertain or not yet known?
- What event has now happened, or become certain not to happen?
- On what exact date did that occur?
- Does the new information make the purchase reportable for the first time?
- Does it mean more tax, less tax or no change?
- What was the effective date of the original purchase?
- Was payment deferred under an HMRC arrangement?
- If several plot sales happened, did they fall in the same calendar month?
This order matters. The original deal and the later event drive the answer.
The payment’s label does not.
Example
Elena buys land for £400,000. Her contract also says she will pay £50,000 if part of the land is later sold as a plot. The plot is sold and the extra £50,000 becomes due.
Elena must recalculate SDLT using the full £450,000 total and the rules that applied when she bought the land. If that creates extra tax, the 30-day further-return rule may apply.
If the original deal had not needed a return but now does, the 14-day rule applies instead.
Why this can be difficult in practice
The hard part is often not the payment date. It is deciding when the amount became fixed.
A contract can make the point at which the amount becomes fixed depend on several linked steps, including a sale, receipt of money or a later adjustment.
Read the sequence closely.
You might think a small later payment can be ignored. It cannot be ignored merely because it is small. The question is whether it changes the SDLT due.
- A payment date may differ from the date the relevant event occurred.
- A plot sale may trigger several separate payments under one contract.
- The original return may have used an estimate that now needs revisiting.
- A lower final amount may mean tax was overpaid rather than underpaid.
- The law excludes rent from this particular adjustment rule.
- A repayment is not automatic: the buyer must amend the return or make a claim.
Where less tax is due, the law allows an amendment during the amendment period. After that, the buyer may make a repayment claim.
If HMRC makes a repayment, interest may be due from the date the tax was paid.
Key takeaways
- A later property payment can change SDLT on the original purchase.
- The deadline is usually 14 or 30 days, depending on the effect of the new information.
- Recalculate using the total price and the rules from the original purchase 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 — how future or unknown payments are valued
- FA 2003 section 77 — which land transactions must be reported
- FA 2003 section 80 — returns and repayments when a payment becomes known
- FA 2003 section 86 — when stamp duty tax payments are due
- FA 2003 section 89 — interest on repayments of overpaid stamp duty
- FA 2003 section 90 — deferring tax on future or unknown payments
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
- HMRC’s manual refers to section 90 for its notification process, while the general statutory rules for a payment becoming known are in section 80.
- The supplied material does not include the regulations that can set the detailed requirements for an accepted payment-deferral arrangement.
- The correct route for a repayment depends on whether the original return can still be amended and on the facts of the transaction.
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 purchase contract and any clause dealing with a future payment
- The original SDLT return and payment record
- Any HMRC deferment reference or acceptance correspondence
- Documents showing the date and amount of each later payment
- A calculation showing the original and revised tax position
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 means you must update your SDLT [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 - how future or unknown payments are valued https://www.legislation.gov.uk/ukpga/2003/14/section/51/2025-11-17 - FA 2003 section 77 - which land transactions must be reported https://www.legislation.gov.uk/ukpga/2003/14/section/77/2025-11-17 - FA 2003 section 80 - returns and repayments when a payment becomes known https://www.legislation.gov.uk/ukpga/2003/14/section/80/2025-11-17 - FA 2003 section 86 - when stamp duty tax payments are due https://www.legislation.gov.uk/ukpga/2003/14/section/86/2025-11-17 - FA 2003 section 89 - interest on repayments of overpaid stamp duty https://www.legislation.gov.uk/ukpga/2003/14/section/89/2025-11-17 - FA 2003 section 90 - deferring tax on future or unknown payments https://www.legislation.gov.uk/ukpga/2003/14/section/90/2025-11-17 HMRC's guidance page on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm50950 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 - HMRC's manual refers to section 90 for its notification process, while the general statutory rules for a payment becoming known are in section 80. - The supplied material does not include the regulations that can set the detailed requirements for an accepted payment-deferral arrangement. - The correct route for a repayment depends on whether the original return can still be amended and on the facts of the transaction. 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 a later payment means you must update your SDLT
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