The HICP is based on the data collected to calculate the CPI. Each Member State supplies indices that are used to calculate sub-indices compatible with COICOP/HICP (classification of individual consumption by purpose, adapted to the needs of the calculation of the harmonised consumer price indices).

The HICP are based on samples that are used to obtain reliable and comparable results, bearing in mind the national diversity of products and prices, as well as changes to retail outlets and products.

As the relative level of consumer expenditure for each good or service varies from country to country, there is no "uniform basket" applicable to all the member States.