Impact analysis on transformation of UK consumer price statistics: January 2026

• We plan to introduce improved data and methods for groceries into our consumer price inflation statistics from February 2026 (published in March 2026) as part of our ongoing improvements.

• These changes will be introduced into the Consumer Prices Index including owner occupiers’ housing costs (CPIH), the Consumer Prices Index (CPI) and the Retail Prices Index (RPI) from February 2026 (published in March 2026), and the Household Cost Indices (HCIs) from February 2026 (published in May 2026); we will not discuss HCI changes in this article.

• In line with our revisions policy, we will not revise previously-published consumer price statistics following the introduction of these improvements in 2026.

• This article presents indicative estimates of the impact of introducing groceries scanner data into UK consumer price statistics.

• The average indicative change to the annual rate between January 2019 and June 2025 from the introduction of groceries scanner data was negative 0.02 percentage points for CPIH and negative 0.03 percentage points for CPI, already controlling for the changes introduced in February 2025.

• The headline annual rates of CPIH, CPI and RPI were impacted to one decimal place in 38, 39 and 47 out of 66 months, respectively.

• Indicative impacts of scanner data at headline level are moderated by groceries accounting for only 12% to 15% of the CPIH, CPI and RPI baskets by weight, and by continued existing in‑store and online collection for around half of the groceries market.

• As expected, indicative impacts were larger for more granular indices, where groceries scanner data have a larger proportion of the total weight.

We are currently undertaking an ambitious programme of transformation across our consumer price statistics. This is to safeguard the production and publication of official statistics that serve the public good, as stated in the Code of Practice for Statistics. This includes:

• identifying new data sources
• improving methods
• developing new systems
• establishing new processes

Our Consumer prices development plan: updated September 2025 and our ONS Plan for Economic Statistics: progress update December 2025 articles outline how we have been delivering improvements over recent years and our plans for further transformation.

We aim to make improvements annually as part of a continuous improvement cycle. In 2023, we made improvements to rail fares, in 2024 we introduced improvements to private rents for Great Britain and second-hand cars, and our previous article on transformation impact analysis described 2025’s improvements to imputation methods, consumption segments and private rents for Northern Ireland.

For 2026 (February 2026 data, published in March 2026), we plan to introduce:

• groceries scanner data
• changes to the sampling of hotel overnight stays and computer games
• the improved measurement of the UK House Price Index (HPI) following improvements to UK HPI’s monthly imputation methods in August 2025

In line with our revisions policy, we will not revise previously-published consumer price statistics following the introduction of these improvements in 2026.

Groceries scanner data

From February 2026 (published in March 2026), we will introduce groceries scanner data into our consumer price inflation statistics. Scanner data will cover approximately 50% of the groceries market, with the remainder continuing to be covered through the existing in-store and online collection.

This introduction follows a year-long parallel run and indicative impact analysis article published in April 2025, providing transparency to users about the potential impact of this upcoming improvement.

There are many benefits to using scanner data compared with current data sources, including improved product and geographical coverage, improved ability to capture price variation within a month, inclusion of more discount types and more granular expenditure information. Sections 3 and 4 of our previous impact analysis article published in April 2025 contains more information on the benefits of using groceries scanner data.

We will adopt multilateral index methods for the grocery scanner data, consistent with our approach for introducing alternative data sources for rail fares in 2023 and second-hand cars in 2024. Our Introducing grocery scanner data into consumer price statistics article and How multilateral index methods help us understand grocery scanner data article provide more information on methods.

These methods allow us to make better use of these data sources and account for dynamic changes in the market and consumer spending habits. Our Overview of how we use scanner data in consumer price inflation statistics article, published alongside this article, provides additional information about the use of groceries scanner data.

This article presents indicative impacts from introducing grocery scanner data only into consumer price statistics, covering the period January 2019 to June 2025. Sections 3 and 4 of our indicative impact analysis article published in April 2025 summarised several benefits from using groceries scanner data, such as improved product coverage and capture of a wider range of promotional discounting.

We also plan to introduce improved data and methods for groceries, hotel overnight stays, computer games and UK House Price Index data simultaneously from February 2026 (published March 2026). For more information, see Section 6: Further improvements.

Our “2025 improvements” baseline series in this analysis represents the consumer price statistics that would have been published if the improvements introduced in February 2025 (published in March 2025, described in our indicative impact analysis article published in January 2025) had instead been introduced in 2019. Therefore, the “2025 improvements” baseline series does not match the corresponding published series.

Our series introducing groceries scanner data represents the consumer price statistics that would have been produced if, in addition to the 2025 improvements, groceries scanner data had also been incorporated into consumer price statistics from 2019. In this series, we use a combination of scanner data and data from our existing price collection for areas of the basket containing groceries.

This means that differences between our series using our 2025 improvements series and series introducing groceries scanner data are from the impact of introducing groceries scanner data only.

Differences between indices with and without scanner data arise from a variety of factors. Our indicative impact analysis article published in April 2025 describes several potential reasons for differences between these two series, including differences in index methodologies and product and spatial coverage, and scanner data’s increased data volumes and improved ability to capture effects of short-term promotions in our inflation statistics.

For each of our consumer prices statistics (the Consumer Prices Index including owner occupiers’ housing costs (CPIH), Consumer Prices Index (CPI) and Retail Prices Index (RPI)), we have assessed the impact of introducing groceries scanner data between January 2019 and June 2025, had the changes been introduced from 2019. These are covered separately throughout this section.

Our indicative impact analysis article published in April 2025 has been superseded by the updated analysis in this release. Results are slightly different to those presented in April 2025’s release because of additional quality assurance that has been undertaken since the previous release (resulting in an average 0.003 percentage point increase to the CPIH annual inflation rate between January 2020 and June 2024) and the inclusion of additional time periods in this updated release.

Figures 1 to 3 show the impact of introducing groceries scanner data on headline annual inflation rates for CPIH, CPI and RPI, respectively, between January 2020 and June 2025. In this analysis, we compare our baseline series including 2025 method improvements with our series including groceries scanner data from January 2019.

Indicative impact on Consumer Prices Index including owner occupiers’ housing costs (CPIH)

Table 1 shows the indicative impact of introducing groceries scanner data on CPIH annual and monthly rates of change, per year, rounded to two decimal places.

The annual rate of change of CPIH was 0.02 percentage points lower on average when groceries scanner data were included between January 2019 and June 2025. However, the impact of groceries scanner data was not consistent and varied in direction across different time periods.

Between January 2020 and December 2021, which was in large part affected by the coronavirus (COVID-19) pandemic, the inclusion of groceries scanner data would have led to the headline annual inflation rate for CPIH being 0.1 percentage points (rounded to one decimal place) higher in 13 out of 24 months.

One factor that could have contributed to this is the better representation of product discounts in scanner data compared with our existing local collection. Research by the Institute for Fiscal Studies: Grocery prices and promotions during the COVID-19 pandemic (PDF, 1.64MB) indicates that a reduction in promotions was an important driver of inflation in the early stages of the pandemic. Since scanner data account for multibuy discounts and many loyalty scheme-related discounts, whereas the existing local collection does not, a reduction in discount prevalence would be better captured in the scanner data and could have contributed to higher annual growth rates.

As part of our quality assurance work, we have carried out in‑depth reviews across several consumption segments. For the consumption segments investigated, the case studies suggested that discounting was the main driver of the impacts, as described in our indicative impact analysis article published in April 2025. There are multiple other possible reasons for differences, which are outlined in our Overview of how we use scanner data in consumer price inflation statistics article.

Between January 2022 and September 2024, the introduction of groceries scanner data would have led to a lower CPIH annual rate (0.1 percentage points lower, to one decimal place) in a majority of months.

This may be explained by increased consumer use of loyalty scheme discounts in this period or consumers switching to purchase goods with lower rates of inflation, either of which would be better captured in the scanner data than existing local collection data and methods.

Between October 2024 and June 2025, the introduction of groceries scanner data would have led to an unchanged headline CPIH annual rate (in five months) or an increase of 0.1 percentage points (in four months), when rounded to one decimal place.

During this period, the CPIH annual rate generally rose, and the average monthly inflation rate was identical to three decimal places (0.398%) for both the CPIH series with and without inclusion of scanner data. This shows that the inclusion of scanner data had minimal impact on CPIH monthly inflation between October 2024 and June 2025. The slight increase in the headline CPIH annual rate in some months of this period from inclusion of groceries scanner data was mainly because of base effects from a year before, rather than from current-period variations.

Indicative impact on Consumer Prices Index (CPI)

Table 2 shows the indicative impact of introducing groceries scanner data on CPI annual and monthly rates of change, per year, rounded to two decimal places.

Figure 2 shows that the annual rate of change for CPI was 0.03 percentage points lower on average when introducing groceries scanner data. The impact of scanner data on the CPI annual rate was very similar to that seen for the Consumer Prices Index including owner occupiers’ housing costs (CPIH), with average impact in the same upwards or downwards direction for CPI during the same three broad periods described previously for CPIH.

Using unrounded data for each monthly period, the impact on the headline annual inflation rate from including groceries scanner data was found to always be both in the same direction and of greater magnitude in CPI than in CPIH. This was reflected in the average impact on the annual rate from the inclusion of groceries scanner data being slightly larger for CPI (negative 0.03 percentage points) than for CPIH (negative 0.02 percentage points). This is expected because the two categories affected by the inclusion of groceries scanner data (“food and non-alcoholic beverages” and “alcoholic beverages and tobacco”) have a slightly larger weight in CPI than in CPIH.

Note that the greater impact on CPI compared with CPIH cannot be clearly seen by comparing Figure 1 and Figure 2 because data within these charts have been rounded to one decimal place to show the indicative impact on the headline CPI (commonly reported at one decimal place).

For more information on the consumer prices weights please see our Consumer price inflation, updating weights: 2025 article.

Indicative impact on Retail Prices Index (RPI)

Table 3 shows the indicative impact of introducing groceries scanner data on RPI annual and monthly rates of change, per year, rounded to two decimal places.

The annual rate of change of RPI was 0.02 percentage points lower on average when introducing grocery scanner data. The average annual growth differences per year for RPI were similar to the Consumer Prices Index (CPI) and Consumer Prices Index including owner occupiers’ housing costs (CPIH) in 2020, 2023, 2024 and 2025, but larger in 2021 and 2022.

Differences between RPI, and CPI and CPIH observed trends were partly caused by imputation differences during the coronavirus (COVID-19) pandemic, because of the different classification systems used for RPI, and CPI and CPIH.

Additionally, the higher weight of the “alcoholic beverages and tobacco” division in RPI compared with the weight of the corresponding category in CPI and CPIH (because of the inclusion of licensed alcohol sales within this division for RPI), also contributes to the differences seen.

Price movements for higher-weighted component indices will have a greater impact on the inflation rate than lower-weighted components. Contributions to the difference in annual rates have been calculated to show the relative contributions of all categories within a given parent category to the difference between the annual rates with and without groceries scanner data (accounting for both the weight and price movement).

These contributions have been calculated by subtracting the contributions to annual rates for indices without groceries scanner data from the contributions to annual rates for indices with groceries scanner data.

Consumer Prices Index including owner occupiers’ housing costs (CPIH)

Figure 4 shows that, although both “food and non-alcoholic beverages” and “alcoholic beverages and tobacco” contributed to the differences in the headline annual rate for the Consumer Prices Index including owner occupiers’ housing costs (CPIH), the contribution of “food and non-alcoholic beverages” to the difference in the headline annual rate was larger. This is in line with expectations, given the weight for “food and non-alcoholic beverages” is more than twice that of the “alcoholic beverages and tobacco” category.

Between March 2020 and November 2021, in the majority of months, both “food and non-alcoholic beverages” and “alcoholic beverages and tobacco” pushed the CPIH annual inflation rate higher when groceries scanner data were included.

Between December 2021 and December 2022, “food and non-alcoholic beverages” tended to push the CPIH annual rate lower, while “alcoholic beverages and tobacco” pushed the CPIH annual rate higher, when groceries scanner data were included.

Between January 2023 and September 2024, “food and non-alcoholic beverages” always pushed the CPIH annual rate lower, and “alcoholic beverages and tobacco” mostly pushed the CPIH annual rate lower, when scanner data were included.

From October 2024, contributions to the difference in the CPIH annual rate were generally smaller with a mixture of both upward and downward impacts. This led to a smaller impact on the headline CPIH annual rate from the inclusion of groceries scanner data in the most recent months compared with older periods, which is reflected in Figure 1.

Consumer Prices Index (CPI)

Figure 5 shows that “food and non-alcoholic beverages” contributed more than “alcoholic beverages and tobacco” to the differences in the headline annual rate for the Consumer Prices Index (CPI) from the inclusion of groceries scanner data. This aligned with that seen for Consumer Prices Index including owner occupiers’ housing costs (CPIH).

As seen with CPIH, when groceries scanner data were included, “food and non-alcoholic beverages” pushed the CPI annual inflation rate higher in the majority of months in 2020 and 2021, and pushed the CPI annual inflation rate lower between 2022 and September 2024.

Differences between RPI, and CPI and CPIH observed trends were driven by imputation differences during the coronavirus (COVID-19) pandemic, because of the different classification systems used for RPI, and CPI and CPIH.

In RPI, indices for licensed alcohol sales were imputed in some months using price movements from the alcoholic drink index, which in January 2021 showed higher monthly growth in the series including scanner data. This pushed the alcoholic drink annual rate upwards in early 2021 in the series including scanner data. A year later, base effects meant that the annual rate for the series including scanner data was lower than the series excluding scanner data in 2022.

In CPI and CPIH, licensed alcohol sales fall within the "restaurants and hotels" division, which is unaffected by groceries scanner data.

Figure 6 shows the relative contributions of the classes within the food group to the difference in annual rate when including and not including groceries scanner data, for the Consumer Prices Index including owner occupiers’ housing costs (CPIH).

Most classes tended to contribute to the difference in a consistent direction for a sustained period. For example, between July 2024 and June 2025, the “bread and cereals” and “meat” classes generally had upward contributions to the difference in the CPIH annual rate for “food”, while “sugar, jam, syrups, chocolate and confectionery” consistently contributed downwards.

In contrast, in the previous 12-month period between July 2023 and June 2024, the “bread and cereals” and “meat” classes generally had downward contributions to the difference in the CPIH annual rate for “food”, while “sugar, jam, syrups, chocolate and confectionery” generally had upward contributions between July 2023 and January 2024, and generally downward contributions between February 2024 and June 2024.

The plans for groceries scanner data outlined in this article will require changes to our consumption segment indices and price quotes microdataset. Specifically, from March 2026, price quote microdata for Divisions 1 and 2 will no longer be published. We recently ran a user feedback survey to understand how they are currently being used. See our response to the user feedback survey. In response to this survey, we have published alongside this article an article on Changes to the provision of microdata outputs for consumer price inflation statistics: January 2026.

In addition to the inclusion of groceries scanner data into our consumer price statistics from February 2026 data (published in March 2026), some other improvements are being made, with smaller impact on headline statistics. This includes introduction of the improved measurement of the UK House Price Index (HPI) and changes to price collection for one-night hotel overnight stays and computer games.

The UK HPI data are used in the Consumer Prices Index (CPI) and Consumer Prices Index including owner occupiers’ housing costs (CPIH) for surveyors’ fees only, and within five items in the Retail Prices Index (RPI). The surveyors’ fees item has a weight of less than 0.2% in 2025 in both CPI and CPIH. The five items have a total weight of around 12% in RPI. The change will take on the improved monthly imputation method introduced into the UK HPI in August 2025. Further information about this UK HPI improvement is available in HM Land Registry’s About the UK HPI guidance.

The changes to computer games affect the items for computer games bought online and computer game downloads, which have a combined weight of less than 0.2% in each of CPI, CPIH and RPI. The indices for these items can be volatile because of the changes in the composition of bestseller charts from month to month. To reduce the volatility and aid interpretation of the data, prices will be collected twice per month.

Similarly, prices of overnight hotel accommodation can be volatile depending on short-term demand and availability of rooms to price. The 2026 changes mean that a hotel price collected six weeks in advance will be collected for two separate nights each month and a hotel price collected one day in advance will be removed from the basket. These items have a total weight of less than 0.9% in CPI, CPIH and RPI.

The indicative impact of these changes, where available, are much smaller than the impact of including groceries scanner data and these 2026 improvements will improve our measure of consumer price inflation by reducing the volatility seen in these items’ indices in the future. Further detail on these improvements is available in the ONS’s Notification of proposed changes to RPI in 2026 letter.

We are in the final stages of testing that we are ready to bring the 2026 improvements discussed in this article into live monthly production. The first time these improvements will be introduced is in the figures for February 2026, published in March 2026. The existing published series will not be revised.

Our broader plans to transform UK consumer price statistics by including new improved data sources and developing our methods and systems are discussed in our Consumer prices development plan: updated September 2025 article.