1. Introduction

In 2026, some changes will take place to the way in which the Consumer Price Index (CPI) and the European Harmonized Index of Consumer Prices (HICP) are calculated and published. It is customary to change the reference year for the CPI and HICP periodically, and this change generally occurs once every ten years. The change to the reference year and the other changes relate to the series for which the reference year is 2025 (i.e. 2025=100). There will be no change to the series on inflation that has already been published with 2015 as reference year (i.e. 2015=100).

Here is a summary of the main changes:

• The most obvious change will be the change of the reference year for the CPI and HICP from 2015=100 to 2025=100. 
• A new system of classifying goods and services will be introduced: the ECOICOP v.2. This is relevant for users of the detailed data.
• Some changes have been made to the methodology used for the CPI. These relate to bungalow parks and package holidays; nursing homes; games of chance; and the price definition of personal contributions for health care and child care. 

Section 2 provides advice on how to use the old and new series for indexing purposes. Previously published figures with the reference year 2015=100 remain available, but this series will no longer be supplemented with new reporting periods.

Section 3 describes the reason for the changes, and explains these in further detail. One important factor is the need for alignment with international definitions and the methods of the HICP. As in 2016, the 2026 changes will eliminate a number of differences. An explanation is also provided as to why the CPI is not yet fully aligned with international definitions. Finally, Section 5 discusses the revision strategy and the recalculation of years already published on the basis of the new ECOICOP v.2.