Understanding Consumer and Retail Prices Index Definitions for LTT Purposes

Meaning of CPI and RPI for Land Transaction Tax

For Land Transaction Tax, the terms “consumer prices index” and “retail prices index” have specific legal meanings. They refer to particular official indexes published by the Statistics Board, so you must use the exact statutory definition rather than any general or alternative measure of inflation.

• “Consumer prices index” means the all items consumer prices index published by the Statistics Board.
• “Retail prices index” means the United Kingdom General Index of Retail Prices published by the Statistics Board.
• If an LTT provision mentions CPI or RPI, use the official index named in the legislation, not another version or informal inflation measure.
• Before applying the rule, check the exact LTT provision, including any required date, period, or comparison point.
• This definition only identifies the correct index; the detailed calculation, timing, and any rounding rules must come from the specific LTT provision being used.

Scroll down for the full analysis.

What “consumer prices index” and “retail prices index” mean for Land Transaction Tax

This page explains the meaning of two inflation measures used in the Land Transaction Tax rules: the consumer prices index and the retail prices index. The point is narrow, but it matters because where LTT legislation refers to either index, it is referring to a specific official published measure, not a general idea of inflation.

What this rule is about

LTT legislation sometimes needs a standard way to measure changes in prices over time. Section 75 identifies exactly what is meant by two commonly used terms:

• consumer prices index
• retail prices index

The purpose is to avoid uncertainty. If the legislation uses one of these terms, readers do not need to guess which version of CPI or RPI is intended.

What the official source says

The official material states that, for LTT purposes:

• the consumer prices index means the all items consumer prices index published by the Statistics Board
• the retail prices index means the United Kingdom General Index of Retail Prices published by the Statistics Board

So the legislation is not using these labels loosely. It ties each term to a particular official index published by the relevant public authority.

What this means in practice

If an LTT provision refers to CPI, you should read that as the all items consumer prices index, not another CPI variant. If it refers to RPI, you should read that as the United Kingdom General Index of Retail Prices, not some other retail-price measure.

This matters where a figure in the legislation is adjusted, compared, uprated, or interpreted by reference to inflation. The correct index must be used. Using a different published inflation measure could produce the wrong result.

In practice, the main point is one of identification. Before doing any calculation or interpretation, check:

• whether the relevant LTT provision refers to CPI or RPI
• whether it specifies a particular date, period, or comparison point
• whether the calculation depends on a published figure from the Statistics Board

How to analyse it

A sensible approach is:

1. Find the exact LTT provision you are applying.
2. Check whether it uses the term consumer prices index or retail prices index.
3. Use the statutory meaning given by section 75, rather than any informal or commercial inflation measure.
4. Check the relevant published index figure for the date or period required by the legislation.
5. Make sure you are using the correct index series: all items CPI for consumer prices index, or the UK General Index of Retail Prices for retail prices index.

The key legal point is that the definition comes from the statute. The practical exercise is then to identify the correct published figure that matches the statutory wording.

Example

Illustration: suppose an LTT rule required a figure to be adjusted by reference to the consumer prices index. You would not choose any inflation measure that seems reasonable. You would use the all items consumer prices index published by the Statistics Board, because that is what the legislation says the term means for LTT purposes.

Why this can be difficult in practice

The wording itself is straightforward, but problems can still arise if a reader assumes that “CPI” or “RPI” is being used in a general sense. Official statistics can exist in different forms or series, and the legal definition may be narrower than everyday usage.

Another practical difficulty is that this provision only defines the terms. It does not, by itself, explain how any adjustment is to be calculated, which dates matter, or what rounding rules apply. Those points would need to come from the specific LTT provision that uses the index.

Key takeaways

• For LTT, consumer prices index means the all items consumer prices index published by the Statistics Board.
• For LTT, retail prices index means the United Kingdom General Index of Retail Prices published by the Statistics Board.
• If an LTT rule refers to CPI or RPI, use the statutory definition and the correct official published series.

This page was last updated on 24 March 2026

Useful article? You may find it helpful to read the original guidance here: Understanding Consumer and Retail Prices Index Definitions for LTT Purposes

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