2. Advice on using CPI series for indexing purposes

Consumer price index figures are often used to adjust contracts and to adjust fees and charges. In this section, Statistics Netherlands (CBS) provides guidance on the use of the various index series that are available.

With effect from February 2026, a new CPI series based on 2025=100 will become available.

The 2015=100 series will be discontinued with effect from the reporting month December 2025, but previously published figures will remain available. In a limited number of cases, the 2025=100 series produces different figures for the changes in the indices compared with the figures previously published on the basis of the 2015=100 series.

In cases where regulations or contracts specify that the consumer price index (CPI) figure is to be used, CBS recommends using the CPI series and not the HICP series, unless the use of the European harmonised consumer price index is explicitly stipulated.

When choosing between using the old and new CPI series, CBS advises the following:

Use the 2015=100 series to determine the price change over a period that ends in or before the year 2025.
Use the 2025=100 series to determine the price change over a period that ends in or after January 2026.

A separate webpage is available on the CBS website with a more detailed explanation of indexations (in Dutch only): Indexations for new contracts | CBS

Examples:

You wish to adjust a contract based on price changes between October 2024 and October 2025 based on the CPI. Use the figures from the 2015=100 series.
You wish to adjust a contract based on price changes between the year 2024 and the year 2025 based on the CPI. Use the figures from the 2015=100 series.
You wish to adjust a contract based on price changes between May 2025 and May 2026 based on the CPI. Use the figures from the 2025=100 series.
You wish to adjust a contract based on price changes between May 2023 and May 2026 based on the CPI. Use the figures from the 2025=100 series.