What CPI and RPI mean for Welsh Land Transaction Tax
CPI and RPI for LTT
For Welsh Land Transaction Tax, CPI and RPI refer to two specific indexes published by the Statistics Board.
- CPI is the all-items Consumer Prices Index
- RPI is the UK General Index of Retail Prices
- The LTT rule using the index decides the relevant date and calculation
Scroll down for the full analysis.
Read the original guidance here:
What CPI and RPI mean for Welsh Land Transaction Tax
If an LTT rule refers to CPI or RPI, it identifies a specific official price index. It does not refer to any inflation figure found online. This distinction can matter when a stamp duty land tax calculation or limit is adjusted over time, because the applicable rule may require one specified measure rather than another. The label controls.
What this rule is about
Land Transaction Tax, or LTT, applies to land purchases in Wales, and a tax rule may use an index where it updates an amount over time. Section 75 makes clear which index name must be used.
Although the names sound alike, they are not interchangeable.
What the official source says
In explaining the relevant terms, the Welsh Government guidance reflects the definitions in section 75 of the LTT Act.
- CPI means the all-items Consumer Prices Index.
- The Statistics Board publishes that index.
- RPI means the United Kingdom General Index of Retail Prices.
- The Statistics Board publishes that index too.
What this means in practice
First, identify the exact term used by the relevant LTT rule. Where it says CPI, use CPI. Where it says RPI, use RPI. Do not replace one with the other merely because both track changes in prices.
- Keep a copy of the relevant official index figure.
- Check the date the LTT rule tells you to use.
- Record whether the rule says CPI or RPI.
How to analyse it
Identifying the index label is only the first step. The rule that refers to it should state what must be worked out.
- Find the LTT provision that uses an index.
- Read whether it names CPI or RPI.
- Check the date or period specified by that provision.
- Use the matching official publication.
Example
Imagine an LTT rule requires an amount to be updated using CPI. You would look for the all-items Consumer Prices Index, not the Retail Prices Index. Where the rule instead says RPI, the result changes because you must use the United Kingdom General Index of Retail Prices.
Why this can be difficult in practice
Finding an index may not be the difficult part. The challenge is reading the separate LTT rule that determines which date applies and how the calculation must be made. This short definition does not provide that method.
- “Inflation” is not enough; the named index matters.
- A current index figure may be wrong if the rule requires an earlier one.
- The guidance does not identify every LTT rule that uses an index.
Key takeaways
- CPI means the all-items Consumer Prices Index.
- RPI means the UK General Index of Retail Prices.
- Always follow the index and date named by the relevant LTT rule.
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 75 — defines the CPI and RPI used in LTT
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
- This source does not identify the particular LTT provisions that may require CPI or RPI, or the relevant publication date for an index figure.
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 LTT provision that calls for CPI or RPI.
- The relevant index publication and the date required by that provision.
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 What CPI and RPI mean for Welsh Land Transaction Tax [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 75 - defines the CPI and RPI used in LTT https://www.legislation.gov.uk/anaw/2017/1/section/75 Guidance page from the Welsh Revenue Authority on this topic (guidance, not law): https://www.gov.wales/land-transaction-tax-interpretation-provisions-technical-guidance#6428 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 - This source does not identify the particular LTT provisions that may require CPI or RPI, or the relevant publication date for an index figure. 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: What CPI and RPI mean for Welsh Land Transaction Tax
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