FOI reference: FOI-2026-3554
You asked
Pursuant to section 1 FOIA, we request the following recorded information held by the ONS:
1. CPI food component – back cast under new methodology
A monthly time series for at least the last five years (or for the full period over which it is available, if longer) of the CPI “food” component index (or “food and non-alcoholic beverages” component, if that is how the ONS structures the series), compiled on a consistent basis using the new supermarket scanner data methodology that has recently been introduced.
2. RPI food component – back cast under new methodology
A corresponding monthly time series for at least the last five years (or for the full period over which it is available, if longer) of the RPI “food” component index, compiled on a consistent basis using the new supermarket scanner data methodology.
3. Underlying datasets / calculations for published impacts
Any datasets, tables, or internal outputs (for example, spreadsheets or databases) used to produce the published estimates of:
the impact of the supermarket food price collection methodology change on headline CPI and RPI inflation; and
the contribution of the food component methodology change to overall CPI and RPI inflation
We said
Thank you for your request.
In answer to your questions 1 and 2, we have published an user-requested dataset on the ONS website, which includes the CPI and RPI “food” component index from January 2019 equals 100. These data contain indicative estimates which underpinned the Impact analysis on transformation of UK consumer price statistics: January 2026 article, which was published at 9:30am on 28 January 2026. These data supplement the impact analysis article and have been released to support user understanding of the indicative impact of introducing groceries scanner data into the ONS's suite of consumer price statistics.
Regarding your question 3, all microdata inputs that we are able to publish are available in our Consumer Price Indices (CPI) and Retail Price Index (RPI) item indices and prices quotes dataset.
While we do hold the raw scanner data on ONS systems, we are unable to disclose this information. The scanner data identifies and relates to individual businesses and we are prohibited by Section 39 of the Statistics and Registration Service Act 2007 (SRSA) from disclosing information from which individual businesses or persons can be identified. As we are prohibited by law from disclosing this information, Section 44(1) of the Freedom of Information Act 2000 (FOIA) applies.