When a later payment means you must file another LTT return
Further LTT returns for later payments
If a property price was conditional or unknown, a later event may require another LTT return to WRA.
- File within 30 days after the relevant event.
- A further return needs a fresh tax calculation.
- Interest may run from shortly after the original transaction date.
Scroll down for the full analysis.
Read the original guidance here:
When a later payment means you must file another LTT return
Your first Land Transaction Tax return may not be the end of the matter if part of your property price was unknown or depended on something happening later. LTT is Wales’s land tax, rather than stamp duty.
Once the amount becomes clear, you may need to send the Welsh Revenue Authority (WRA) another return within 30 days. This applies if the clarification changes whether the deal is reportable or alters the LTT due. Act promptly.
What this rule is about
In some property deals, buyers cannot fix the price on completion day. For example, a seller may receive an extra sum if planning permission is granted, or the final sum may depend on accounts prepared later.
You still deal with LTT at the start. The law uses a reasonable estimate for an unknown amount. For a conditional payment, it uses a set assumption about the outcome of that condition.
Later, the missing fact may arrive. That can change the tax bill.
What the official source says
WRA’s technical guidance explains the duty in section 47. The guidance is not the law itself; section 47 of the Land Transaction Tax and Anti-avoidance of Devolved Taxes (Wales) Act 2017 sets the legal rule.
A buyer must make a further return when a relevant event happens and it changes the tax position in one of the ways set out below.
- A condition affecting a later payment happens.
- It becomes clear that the condition will not happen.
- An amount used to work out the price becomes known.
- An instalment of the price becomes known.
- The event makes a transaction reportable when it was not reportable before.
- The event means more LTT is due.
- The event means LTT is due where none was due before.
The further return must include your own calculation of the LTT due. You must file it within 30 days, starting with the day after the relevant event.
There is an important limit: this rule does not apply to rent. It also does not apply to an annuity covered by the separate statutory rules.
What this means in practice
A later payment alone does not automatically require another return. It must also change whether the deal is reportable or change the LTT due.
Do not wait until the money is physically paid if the amount was known earlier. The clock runs from the event that settles the condition or amount.
- Keep the original LTT calculation and the estimate behind it.
- Watch for planning decisions, account sign-off, valuations and other trigger events.
- Record the exact date when the amount became known.
- Compare the final position with the return already filed.
- File a further return if one of the statutory triggers applies.
- Include a fresh calculation of the tax in that return.
Interest is the part people often miss. Where extra tax is due, the interest clock can start shortly after the original transaction date, not when the price later becomes clear.
How to analyse it
Begin with the deal documents rather than the label given to the payment. Describing a sum as a bonus, adjustment or deferred payment does not settle the issue.
- Was any part of the price conditional, unknown or not yet worked out at completion?
- What estimate or assumption was used in the original LTT return?
- Did a condition happen, fail, or become certain not to happen?
- When did the relevant amount become known?
- Does that event change the amount of LTT due?
- Does it turn a previously non-reportable deal into a reportable one?
- Is the payment rent or an annuity, which this rule excludes?
- Has the 30-day filing period started?
Connected deals require one extra check. Section 47 can also cover an uncertain amount concerning a linked transaction, rather than only the particular purchase under review.
Example
Sam buys land on 1 July for £300,000, plus a further amount based on figures that the parties will settle later. Sam uses a reasonable estimate in the original LTT return.
On 12 September, the final figures show that the total price is £340,000. If that increase results in more LTT being due, Sam must file a further return by 12 October.
The later figures do not create the tax from scratch. They settle part of the original price.
If extra tax is due, interest may start from 1 August: the day after the 30-day period following the 1 July transaction date.
Why this can be difficult in practice
The arithmetic is often not the hard question. Instead, the difficulty is deciding what the contract meant at the time of the purchase.
A payment can be genuinely uncertain, while a fixed agreement may simply require another payment later. The contract, completion statement, correspondence and later evidence can all matter.
- A vague contract may make the trigger date hard to identify.
- Accounts can be prepared before they are finally agreed.
- A planning condition may be satisfied in stages.
- A buyer may wrongly assume that no further return is needed until cash changes hands.
- A buyer may overlook interest because the later event happened months after completion.
If you only remember one thing, make it this: identify the event that fixed the amount, then check the 30-day deadline straight away.
Key takeaways
- An unknown or conditional price may require a later LTT return.
- The return is only required if the later event changes the tax position.
- Extra tax can carry interest from shortly after 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
- LTTA 2017 section 19 — how to value a contingent part of the price
- LTTA 2017 section 20 — reasonable estimates for unknown purchase prices
- LTTA 2017 section 21 — special treatment of long-term periodic payments
- LTTA 2017 section 47 — further returns when a price becomes known
Official guidance
The pages below are the Welsh Revenue Authority’s guidance. Guidance is not law. It sets out how the Welsh Revenue Authority 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. the Welsh Revenue Authority can also change or withdraw guidance, and it may not cover your facts.
Where this is not settled
- It can be difficult to decide whether a later payment was genuinely uncertain or conditional when the purchase completed.
- The date when an amount became known, or when it became clear that a condition would not happen, can depend on the documents and 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 purchase contract and any side agreement about later payments.
- Records showing the estimate used in the original LTT return.
- Evidence of the event that settled the amount or ended the condition.
- A calculation showing whether the event changes the LTT position.
- The effective date of the original property transaction.
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 Land Transaction Tax (LTT), the tax on property in Wales. It replaced Stamp Duty Land Tax in Wales on 1 April 2018, and SDLT does not apply in Wales. MY QUESTION When a later payment means you must file another LTT 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 - LTTA 2017 section 19 - how to value a contingent part of the price https://www.legislation.gov.uk/anaw/2017/1/section/19 - LTTA 2017 section 20 - reasonable estimates for unknown purchase prices https://www.legislation.gov.uk/anaw/2017/1/section/20 - LTTA 2017 section 21 - special treatment of long-term periodic payments https://www.legislation.gov.uk/anaw/2017/1/section/21 - LTTA 2017 section 47 - further returns when a price becomes known https://www.legislation.gov.uk/anaw/2017/1/section/47 Guidance page from the Welsh Revenue Authority on this topic (guidance, not law): https://www.gov.wales/land-transaction-tax-returns-and-payments-technical-guidance#5554 HOW I WANT YOU TO ANSWER 1. Work from the legislation above. Read it before answering. Guidance from the Welsh Revenue Authority 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 difficult to decide whether a later payment was genuinely uncertain or conditional when the purchase completed. - The date when an amount became known, or when it became clear that a condition would not happen, can depend on the documents and facts. Do not give me a conclusion you cannot support from the provisions above.
Legislation links show the Land Transaction Tax and Anti-avoidance of Devolved Taxes (Wales) Act 2017 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 3 September 2026
Useful article? You may find it helpful to read the original guidance here: When a later payment means you must file another LTT return
Search Land Tax Advice with Google
